JP7608793B2 - LIQUID EJECTION APPARATUS, LIQUID EJECTION METHOD, AND PROGRAM - Google Patents

Description

The present invention relates to a liquid ejection device, a liquid ejection method, and a program.

In inkjet liquid ejection devices (inkjet recording devices), a technology has been developed for multi-scan printing (multi-scan recording) processing in which data is created for each scan using multiple masks for dot data after halftone processing. In mask processing, masks are used as overlap processing in which ejected dots of the same color in the image formed by actual printing partially overlap, as void processing in which dots are not formed regardless of the presence or absence of dot data, or as a combination of overlap processing and void processing. This technology can suppress image defects such as banding and streaks caused by misalignment of dot landing positions, and can increase the amount of ink deposition beyond the number of dots in the data.

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

The present invention has been made in consideration of the above, and aims to provide a liquid ejection device, a liquid ejection method, and a program that can further improve image quality.

In order to solve the above-mentioned problems and achieve the object, the present invention comprises 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 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 that uses the overlapping dot information assigned to each dot of the dot data and a printing discrimination mask to generate scan data that indicates whether or not liquid is 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 that 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.

The present invention has the effect of further improving image quality.

FIG. 1 is a diagram showing an example of a schematic configuration of an inkjet recording apparatus according to the present embodiment. FIG. 2 is a diagram showing an example of a hardware configuration of the inkjet recording apparatus according to the present embodiment. FIG. 3 is a diagram showing an example of the functional block configuration of the inkjet recording apparatus according to the present embodiment. FIG. 4 is a diagram showing an example of a multi-pass printing process in a serial type inkjet recording apparatus. FIG. 5 is a diagram showing an example of a flowchart of data processing during multi-pass printing processing. FIG. 6 is a diagram for explaining the basic stroke-selection process. FIG. 7 is a diagram showing an example of 2-pass 1/4 interlace. FIG. 8 is a diagram for explaining the shot separation process when the overlap gap process is performed. FIG. 9 is a diagram for explaining the effect of the overlapping process and the gap processing on density unevenness. FIG. 10 is a graph showing the overlap ratio versus gradation. FIG. 11 is a diagram showing an example of dot arrangement when overlapping processing is performed or not in a low gradation portion and when landing deviation occurs. 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. 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. 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. 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. FIG. 16 is a diagram for explaining an example of the printing process in the inkjet printing apparatus according to the present embodiment. 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.

Embodiments of a liquid ejection device, a liquid ejection method, and a program are described in detail below with reference to the attached drawings.

The inkjet recording device, which is an example of a liquid ejection device according to this 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 or UV-curable inks 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 this 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 can be any color.

Figure 1 is a diagram showing an example of a schematic configuration of an inkjet recording device according to this embodiment. The schematic configuration of the inkjet recording device 10 according to this embodiment will be described with reference to Figure 1.

As shown in FIG. 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 the main scanning direction. The inkjet recording device 10 includes a carriage 11 that moves back and forth (bidirectional scanning) in both the forward direction 21 and the return 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.

The carriage 11 carries a head unit 12 having multiple ejection heads that eject ink (an example of liquid). The carriage 11 also scans in a direction (main scanning direction) perpendicular to the transport direction (sub-scanning direction) of the recording medium 14 to form an image. Note that the recording medium 14 is not limited to paper.

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.

The transport stage 13 is a platform that is positioned 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. In other words, the inkjet recording device 10 can form a desired image on the recording medium 14 by moving the carriage 11 and ejecting ink droplets from the head unit 12 onto the recording medium 14.

Figure 2 is a diagram showing an example of the hardware configuration of an inkjet recording device according to this embodiment. The hardware configuration of the inkjet recording device 10 according to this embodiment will be described with reference to Figure 2.

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

The main control board 120 is a board that controls the operation of various devices within the inkjet recording device 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 drive circuit 124, a main scanning drive circuit 125, a sub-scanning drive circuit 126, a communication I/F 127, and a control FPGA (Field Programmable Gate Array) 130.

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 is equipped with the head unit 12, an encoder sensor 15, and a print sensor 18.

The CPU 121 is a calculation device that is responsible for the overall control of the inkjet recording device 10. For example, the CPU 121 uses the RAM 123 as a working area to execute various control programs stored in the ROM 122 and output control commands for controlling various operations in the inkjet recording device 10.

The recording head drive circuit 124 is a drive circuit that drives the head unit 12 to perform an ejection 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.

The communication I/F 127 is an interface for connecting the inkjet recording device 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 device 10 from the external device 30. Note that in FIG. 2, the communication I/F 127 of the inkjet recording device 10 is directly connected to the external device 30, but this 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 via wireless communication.

The control FPGA 130 is an integrated circuit that cooperates with the CPU 121 to control various operations in the inkjet recording device 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.

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

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

The sensor control unit 133 performs processing to input the encoder value output from the encoder sensor 15 and the image data read by the print sensor 18.

The head unit 12 is driven by a recording head drive circuit 124, the operation of which 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.

The encoder sensor 15 is a sensor that detects marks on an encoder sheet (not shown) and outputs the obtained encoder value 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.

The print sensor 18 is a sensor that reads the image printed by the head unit 12, for example, to detect the ejection status of each nozzle in the nozzle row.

Note that the hardware configuration of the inkjet recording device 10 shown in FIG. 2 is an example, and may include components other than those shown in FIG. 2.

Figure 3 shows an example of the functional block configuration of an inkjet recording device according to this embodiment.

As shown in FIG. 3, the inkjet recording device 10 has 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.

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 a program executed by the CPU 121.

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 a process 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.

The rendering processing unit 142 is a functional unit that performs rendering processing. Here, rendering processing refers to processing that determines how to move the head unit 12 and 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 execution of a program by the CPU 121.

The image formation end determination unit 143 is a functional unit that determines the end of the printing operation controlled by the image formation 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.

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 to control the movement of the carriage 11 in the main scanning direction. In addition, the motor control unit 144 controls the operation of the sub-scanning drive circuit 126 under the control of the image forming unit 145, thereby controlling the sub-scanning motor 17 driven by the sub-scanning drive circuit 126 to control 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 by the CPU 121 executing a program.

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 drive circuit 124 to control the timing of ink droplet ejection from the head unit 12 driven by the recording head drive 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.

The storage unit 146 is a functional unit that stores multiple mask patterns required for the image processing unit 141 to perform the printing dot distribution process. The multiple mask patterns will be described later. The storage unit 146 is realized by a storage device such as the ROM 122 or RAM 123 shown in FIG. 2.

The image processing unit 141 has a color-specific data generation processing unit 151, a first quantization processing unit 152, and a second quantization processing unit 153.

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 that the inkjet recording device 10 can handle. The first quantization processing unit 152 generates dot data that the inkjet recording device 10 can handle 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 adds overlapping dot information indicating whether or not the dot is to be overlapped (an example of overlapping recording) for each dot of the dot data based on the pattern of the dot data generated by the first quantization processing unit 152.

The rendering processing unit 142 also has a shot processing unit 154. The shot processing unit 154 generates print data (an example of scan data) using overlapping dot information assigned to each dot of the dot data and a mask pattern (an example of a shot mask) for the shot processing. Here, the print data is an example of scan data indicating whether or not ink is ejected for each scan by the nozzle in the multi-pass printing process. The multi-pass printing process is also an example of a multi-pass recording process 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 shot processing unit 154 and executes the multi-pass printing process on the recording medium 14. The head unit 12 can eject one or more types of droplets with different volumes, such as large droplets, medium droplets, small droplets, and no ejection, by applying a drive waveform based on the scan data.

Figure 4 shows an example of multi-pass printing processing in a serial type inkjet recording device, and Figure 5 shows an example of a flowchart of data processing during multi-pass printing processing.

As shown in FIG. 4, an example of multi-pass printing processing in a serial inkjet recording device 10 is described here. Multi-scan printing processing is a printing method in which dots are arranged in a divided manner across multiple scans in a serial inkjet recording device 10, and the relative positions of the media and nozzles are shifted for each scan to form an image with the desired resolution.

Figure 4 is an example of 2-pass 1/4 interlace. When 2-pass 1/4 interlace is used, 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 Figure 4 are printed by the nozzle 42 of the head 41 at the same scan line position in the first and fifth scans. Therefore, the dots to be printed in each of the first and fifth scans are separated, and the scan line can be completed by printing the dots separately in each scan.

As shown in Figures 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.

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

Figure 6 explains the basic printing process, and Figure 7 shows an example of 2-pass 1/4 interlace.

Below, we will explain the basic printing process, where the four values of the dot data are when the droplets are large, medium, small, and no ejection. The printing process obtains data corresponding to the nozzle position during each scan from the created dot data, and then performs the printing process on the obtained data.

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, the 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.

As shown in Figure 7, the printing process in Figure 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, a dot arrangement that is the same as the dot data is formed.

Table 1 below shows an example of a printing process using a binary mask pattern. In this case, for example, the mask process calculates the logical product (AND) of the mask value at the corresponding position to the dot data. The mask pattern is binary, and for the dot data of no ejection "00", small droplet "01", medium droplet "10", and large droplet "11", the pixel that does not eject "00" and the pixel that ejects "11" are set. The size of the ink droplet to be output is then determined by calculating the logical product (AND) of the dot data and the mask pattern. In other words, 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 pixel that ejects "01", "10", and "11" are output as is.

Figure 8 is a diagram explaining the printing process when overlapping processing is performed.

As shown in Figure 8, the printing process in Figure 8 is an explanation of the printing process when overlapping processing is performed. In order to suppress uneven density caused by deviations in the landing position of ink droplets, there is a printing process called overlapping processing in which some dots are overlapped. In this case, Figure 8 is an example of 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.

In the printing process using overlapping processing in Figure 8, the mask pattern for 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 printing process overlap, overlapping dots (thick "1") are formed. Alternatively, pixels where no dots are ejected (thick "0") are generated. 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.

Figure 9 is a diagram that explains the effect of overlay processing on density unevenness.

As shown in Figure 9, in the printing process that includes overlapping processing, 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 overlapping processing at this time.

Figure 9 (1) is an example when overlapping processing is not performed, and when the landing position of the ink droplets is shifted, the dots of the first half scan and some of the dots of the second half scan overlap, creating unintended blank spaces and leading to uneven density. On the other hand, Figure 9 (2) is an example when overlapping processing is performed, and when the landing position of the ink droplets is shifted, blank spaces are created due to the landing shift, but one side of the overlapping dots fills in the blank spaces caused by the landing position shift, so the difference in ink coverage area is smaller than when overlapping processing is not performed, and there is an effect of suppressing uneven density.

Figure 10 is a graph showing the overlap rate for each gradation, and Figure 11 is a diagram showing an example of dot arrangement when overlap processing is performed in low gradation areas and when impact deviation occurs.

As shown in FIG. 10, this graph shows the ratio of each droplet used in the gradation of image data and the overlap 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 and dotted line indicates the overlap dot rate. Conventional overlapping processes were performed by overlapping the values of some pixels in the mask pattern of the printing process. Therefore, regardless of the type of droplet or gradation, the overlap rate of dots was constant for each 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.

As shown in Figure 11, in the printing process that includes overlapping processing, 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 in the low gradation area with and without overlapping processing.

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, dots are less likely to overlap and density unevenness is less likely 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 the overlapping dots shifts, causing the ink coverage area on one pixel to increase, which can worsen the graininess.

Figures 12 to 14 are diagrams for explaining an example of the process of providing overlapping dot information in an inkjet recording device according to this embodiment. Next, an example of the process of providing overlapping dot information in an inkjet recording device 10 according to this embodiment will be explained using Figures 12 to 14.

The first quantization processing unit 152 generates four-value dot data for large, medium, small, and no droplets based on the color-specific data for each CMYK, as shown in FIG. 12 (1). Next, the second quantization processing unit 153 divides the dot data into multiple regions (e.g., regions 1 to 8) as shown in FIG. 12 (2). The second quantization processing unit 153 then calculates the amount of ink attached (hereinafter referred to as ink attachment amount) M for each of the multiple regions of the dot data.

The second quantization processing unit 153 also assigns overlapping dot information to each dot in each area of the dot data based on the amount of ink adhesion M in that area, as shown in FIG. 13. In this embodiment, the second quantization processing unit 153 assigns overlapping dot information so that the number of overlapping dots decreases as the amount of ink adhesion M decreases.

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

In this embodiment, the second quantization processing unit 153 selects overlapping dot information imparting mask 1 for areas where the ink adhesion amount M is 25 or more, as shown in FIG. 13. Also, the 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, as shown in FIG. 13. Also, the 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, as shown in FIG. 13.

Then, as shown in FIG. 14, the 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. In other words, the 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.

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

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 (overlap dot rate) for dots with low gradation (for example, dots of small droplets with a small amount of ink attached 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 (overlap dot rate) for dots with high gradation (for example, dots of medium and large droplets with a large amount of ink attached 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, which causes 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.

Fig. 16 is a diagram for explaining an example of the printing process in the inkjet recording device according to this embodiment. Fig. 17 is a diagram for explaining an example of the printing process by 2-pass 1/4 interlace in the inkjet recording device 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 printing process unit 154 obtains data corresponding to the nozzle position at the time of each scan from the created dot data, and performs printing process on the obtained data.

As shown in Figure 16, the printing process in Figure 16 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, "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.

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

The inkjet recording device 10 according to the present embodiment can prevent the position of overlapping dots from shifting in low gradation areas and causing a worsening of graininess when overlapping processing is performed. As a result, the image quality can be further improved when overlapping processing is performed.

In the above embodiment, the liquid ejection device of the present invention is applied to an inkjet recording device 10, but it can also be applied to any of multifunction devices, printers, scanner devices, facsimile devices, etc.

In the above-described embodiment, the recording medium 14 is a medium such as paper, recording paper, film, cloth, electronic circuit boards, electronic components such as piezoelectric elements, powder layers, organ models, and test cells, 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, and ceramics.

The liquid may be any liquid having a viscosity and surface tension that allows it to be ejected from a liquid ejection head, such as inkjet ink, surface treatment liquid, liquid for forming components of electronic elements or light-emitting elements or electronic circuit resist patterns, or liquid material for three-dimensional modeling.

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

Furthermore, the program executed by the inkjet recording device 10 of this embodiment may be configured to be stored on a computer connected to a network such as the Internet and provided by downloading it via the network. Also, the program executed by the inkjet recording device 10 of this embodiment may be configured to be provided or distributed via a network such as the Internet.

The program executed by the inkjet recording device 10 of this embodiment has a modular structure including the above-mentioned units (image acquisition unit 140, image processing unit 141, rendering processing unit 142, image formation end determination unit 143, motor control unit 144, image forming unit 145), and in terms of actual hardware, the CPU 121 (an example of a processor) reads the program from the ROM 122 and executes it, thereby loading the above-mentioned units onto the main storage device, and the image acquisition unit 140, image processing unit 141, rendering processing unit 142, image formation end determination unit 143, motor control unit 144, image forming unit 145) are generated on the main storage device.

REFERENCE SIGNS LIST 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 unit 142 Rendering processing unit 143 Image formation end determination unit 144 Motor control unit 145 Image forming unit 146 Storage unit

Patent No. 5328505

Claims (3)

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 . 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 . 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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