JP2021146692A - Liquid discharge device, image processing method and program - Google Patents

Abstract

To flexibly perform adjustment in multi-pass recording.SOLUTION: A liquid discharge device comprises: a mask processing unit which performs mask processing for setting droplet hitting possibility for each print pixel of a print image printed with multi-pass recording on the basis of mask data; and a discharge control unit which controls a discharge unit for discharging liquid on the basis of the result of the mask processing. The mask data includes: first mask data in which thresholds are arranged in a prescribed ascending order pattern on a matrix corresponding to the print pixel; and second mask data in which thresholds are arranged in a reverse ascending order pattern that is reverse to the ascending order pattern on the matrix.SELECTED DRAWING: Figure 5

Description

The present invention relates to a liquid discharge device, an image processing method and a program.

In a liquid ejection device such as an inkjet printer, multipath recording is used in which a nozzle for ejecting a liquid such as ink scans the same area on a medium a plurality of times to form an image. Further, in multi-pass recording, a mask process is performed for setting whether or not the droplet can be dropped by the nozzle for each scan.

For example, for the purpose of improving image quality, a technique for setting halftone conditions so that all of a plurality of dot groups formed by a plurality of nozzle groups that eject ink of the same color have predetermined characteristics is disclosed. (Patent Document 1).

When performing multi-pass recording, mutual complementation that complements the droplets on the print area (print pixel) by multiple nozzles, overstrike that performs multiple droplets on the same print area, and droplets on a specific print area. In some cases, thinning, etc. may be performed. By appropriately adjusting such mutual complementation, overstrike, thinning, etc., it is possible to suppress the occurrence of defects such as banding and graininess. However, in the prior art, it is difficult to flexibly make adjustments in multipath recording.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to enable flexible adjustment in multipath recording.

In order to solve the above-mentioned problems and achieve the object, the liquid discharge device according to the present invention is a mask process that sets whether or not to drip each print pixel printed by multi-pass recording based on mask data. A mask processing unit that performs mask processing and a discharge control unit that controls a discharge unit that discharges liquid based on the result of mask processing are provided, and mask data is obtained in an ascending order pattern in which a threshold value is predetermined on a matrix corresponding to print pixels. It is characterized by including the arranged first mask data and the second mask data arranged on the matrix in a reverse ascending order pattern whose threshold value is opposite to that of the ascending order pattern.

According to the present invention, it is possible to flexibly make adjustments in multipath recording.

FIG. 1 is a block diagram showing an example of the hardware configuration of the liquid discharge device according to the embodiment. FIG. 2 is a diagram showing an example of the configuration of the liquid discharge head. FIG. 3 is a diagram showing an example of the relationship between the nozzle pitch and the recording resolution. FIG. 4 is a diagram showing an example of mask processing in 2-pass 4-interlaced recording. FIG. 5 is a block diagram showing an example of the functional configuration of the liquid discharge device. FIG. 6 is a flowchart showing an example of the processing flow in the liquid discharge device. FIG. 7 is a diagram showing an example of mask data. FIG. 8 is a diagram showing a first example of setting mask data. FIG. 9 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 8 and a final dropping permission range. FIG. 10 is a diagram showing a second example of setting mask data. FIG. 11 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 10 and a final dropping permission range. FIG. 12 is a diagram showing a third example of setting mask data. FIG. 13 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 12 and a final dropping permission range. FIG. 14 is a diagram showing a fourth example of setting mask data. FIG. 15 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 14 and a final dropping permission range. FIG. 16 is a diagram showing a first example of setting mask data when the main scanning path is divided into four. FIG. 17 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 16 and a final dropping permission range. FIG. 18 is a diagram showing a second example of setting mask data when the main scanning path is divided into four. FIG. 19 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 18 and a final dropping permission range. FIG. 20 is a diagram showing a third example of setting mask data when the main scanning path is divided into four. FIG. 21 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 20 and a final dropping permission range. FIG. 22 is a diagram showing a fourth example of setting mask data when the main scanning path is divided into four. FIG. 23 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 22 and a final dropping permission range. FIG. 24 is a diagram showing an example of the correspondence between the FM mask data, the first mask data, and the second mask data used in the halftone processing. FIG. 25 is a diagram showing an example of a dot generation result when rendering is performed by applying the first and second mask data shown in FIG. 24. FIG. 26 is a diagram showing an example of the configuration of the liquid discharge head according to the modified example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an example of the hardware configuration of the liquid discharge device 1 according to the embodiment. Here, the configuration of an inkjet printer will be described as an example of the liquid ejection device 1.

The liquid discharge device 1 includes a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, an NVRAM (Non-Volatile Random Access Memory) 14, an external device connection I / F18, and a network I. / F19 and bus line 20 are provided. Further, the liquid ejection device 1 includes a paper transport unit 21, a sub-scanning driver 22, a main scanning driver 23, a carriage 30, and an operation panel 40. The carriage 30 includes a liquid discharge head 31 (discharge unit) and a liquid discharge head driver 32.

The CPU 11 controls the operation of the entire liquid discharge device 1. The ROM 12 stores a program or the like used to drive the CPU 11 such as an IPL. The RAM 13 is used as a work area of the CPU 11. The NVRAM 14 stores various data such as a program, and holds various data even while the power supply of the liquid discharge device 1 is cut off. The external device connection I / F16 is connected to a PC (Personal Computer) by a USB (Universal Serial Bus) cable or the like, and communicates control signals and printed data with the PC. The network I / F19 is an interface for data communication using a communication network such as the Internet. The bus line 20 is an address bus, a data bus, or the like for electrically connecting each component such as the CPU 11.

The paper transport unit 21 is, for example, a roller and a motor that drives the rollers, and transports printing paper in the sub-scanning direction along a transport path in the liquid ejection device 1. The sub-scanning driver 22 controls the movement of the paper transport unit 21 in the sub-scanning direction. The main scanning driver 23 controls the movement of the carriage 30 in the main scanning direction.

The liquid ejection head 31 of the carriage 30 has a plurality of nozzles for ejecting a liquid such as ink, and is mounted on the carriage 30 so that the ejection surface (nozzle surface) faces the printing paper side. .. The liquid ejection head 31 ejects the liquid to a predetermined position on the printing paper by ejecting the liquid onto the printing paper (an example of the medium) intermittently conveyed in the sub-scanning direction while moving in the main scanning direction. Record the image. The liquid discharge head driver 32 is a driver for controlling the drive of the liquid discharge head 31.

The operation panel 40 is composed of a touch panel, an alarm lamp, or the like that displays the current set value, selection screen, or the like and receives input from the operator.

The liquid discharge head driver 32 may not be mounted on the carriage 30 but may be configured to be connected to the bus line 20 outside the carriage 30. Further, the main scanning driver 23, the sub scanning driver 22, and the liquid discharge head driver 32 may each have a function realized by a command of the CPU 11 according to the program.

FIG. 2 is a diagram showing an example of the configuration of the liquid discharge head 31. The liquid discharge head 31 illustrated here is a so-called serial type inkjet head, and includes a nozzle set including a plurality of nozzles (four in this example) for each of four colors (for example, CMYK). Multipath recording can be executed by appropriately moving the liquid discharge head 31 in the main scanning direction or the sub-scanning direction. By performing multipath recording, it is possible to record (print) at a recording resolution that exceeds the nozzle pitch (nozzle mounting density) between nozzles of the same color. In addition, when performing multi-pass recording, by performing mask processing that sets permission / prohibition of droplets on a predetermined print pixel, mutual complementation that complements the droplets on the print area (print pixel) by a plurality of nozzles. , It is possible to perform overstrike in which droplets are applied a plurality of times to the same print area, thinning in which droplets are not applied to a specific print area, and the like.

FIG. 3 is a diagram showing an example of the relationship between the nozzle pitch and the recording resolution. In FIG. 3, the figure on the left shows a part of a nozzle set that ejects ink of the same color, the figure in the center shows the pixels at the recording resolution and the nozzle position of each scan, and the figure on the right shows each in the multipath recording sequence. It shows the position of the nozzle in scanning.

In the example shown in FIG. 3, the nozzle pitch (150 npi) is lower than the recording resolution (600 dpi). In such a case, in order to record at the corresponding pixel position between the nozzle pitches, the printing paper is moved in the sub-scanning direction by at least the number obtained by "recording resolution / nozzle pitch = number of interlaces", and the nozzle position is recorded. It is necessary to move to the pixel position (the position of the number in the center figure). In the example shown in FIG. 3, four interlacing operations are required. Further, in order to average the injection bending and the discharge amount fluctuation peculiar to each nozzle, in the example shown in FIG. 3, the main scanning direction (direction orthogonal to the nozzle row) is also divided twice (2 passes). .. Instead of completing the recording in the main scanning direction with one nozzle, the recording in the main scanning direction is completed by dropping droplets from another nozzle again. Control that combines paths and interlaces in this way is called "2-pass 4-interlaced recording" in multipath recording.

FIG. 4 is a diagram showing an example of mask processing in 2-pass 4-interlaced recording. In FIG. 4, the mask pattern shown on the right side masks the non-droppable pixels existing at each scan. Here, a "2x4" mask pattern, which is the minimum combination of 2-pass and 4-interlace, is illustrated. Since the mask pattern illustrated here is small with respect to the entire recorded image, it is repeatedly applied in each of the main scan and the sub scan directions.

FIG. 5 is a block diagram showing an example of the functional configuration of the liquid discharge device 1. The liquid discharge device 1 includes a discharge unit 101, a scanning unit 102, a color processing unit 103, a halftone processing unit 104, a rendering unit 105, and a discharge control unit 106. The rendering unit 105 has a mask processing unit 111 and a setting unit 112. These functional units 101-106, 111, 112 are realized by the cooperation of various hardware components shown in FIG. 1, programs stored in ROM 12 and NVRAM 14, and the like.

The ejection unit 101 ejects a liquid such as ink to a medium such as printing paper. The discharge unit 101 includes a liquid discharge head 31, a liquid discharge head driver 32, and the like.

The scanning unit 102 changes the relative position between the ejection unit 101 and the medium so that multipath recording is performed. The scanning unit 102 displaces the ejection unit 101 and / and the medium so that, for example, the ejection unit 101 scans the same region on the medium a plurality of times. The scanning unit 102 includes a carriage 30, a main scanning driver 23, a sub-scanning driver 22, a paper transport unit 21, and the like.

The color processing unit 103 converts the color space of the original image into a color space corresponding to the ink color mounted on the ejection unit 101. The color processing unit 103 is composed of a CPU 11, a program, and the like.

The halftone processing unit 104 uses image data indicating pixel values and the like for each pixel constituting the original image as dot data (print data) indicating the necessity of dropping for each print pixel constituting the print image to be printed on the medium. To generate. The halftone processing unit 104 converts, for example, image data having an m value (256 gradations or more including 0) into dot data having an n value (an integer of 1 or more such that m> n) that can be discharged from the discharge unit 101. do. The halftone processing unit 104 may generate dot data by using FM (Frequency Modulation) mask data or the like. The halftone processing unit 104 is composed of a CPU 11, a program, and the like.

The rendering unit 105 converts the dot data generated by the halftone processing unit 104 into data that matches the configuration (for example, the number of nozzles, nozzle pitch, etc.) and operation (for example, multipath recording, etc.) of the ejection unit 101.

The mask processing unit 111 performs mask processing for setting whether or not dripping is possible for each print pixel of the print image printed by multipath recording based on the mask data described later.

The setting unit 112 can set a range of threshold values for permitting or prohibiting droplets in multipath recording. The setting unit 112 sets the settings related to mutual complementation in which drops are complemented to the print area by a plurality of nozzles, the setting related to overstrike in which the same print pixel is dropped a plurality of times, and the drop is dropped on a specific print pixel. Enables settings related to thinning without performing.

The rendering unit 105, the mask processing unit 111, and the setting unit 112 are composed of a CPU 11, a program, and the like.

The discharge control unit 106 controls the discharge unit 101 based on the result of processing by the rendering unit 105 (including the result of processing by the mask processing unit 111). The discharge control unit 106 includes a CPU 11, a liquid discharge head driver 32, a program, and the like.

FIG. 6 is a flowchart showing an example of the processing flow in the liquid discharge device 1. When the print instruction and the image data are transmitted to the liquid discharge device 1 from the application installed on the PC connected via the network I / F 19, the resolution change process is executed (S101). The display resolution of image data handled on a PC is often lower than the final recording resolution, and may include information composed of intangible outline fonts and vector data. Therefore, conversion to bitmap data and UP conversion of the resolution are performed according to the recording resolution. In rare cases, the resolution may be DOWN converted.

Next, the color conversion process is performed (S102). Since the image data handled on the PC is usually composed of RGB color system color information, color conversion is performed to the CMYK (+ special color) color system according to the CMYK system ink handled by the liquid ejection device 1. Will be. Further, when image data having CMYK color information is input from the beginning, color conversion of the same color system of "CMYK → C'M'Y'K'" is performed. C'M'Y'K'is a standard that matches the color development of the mounted ink. Spot colors refer to colors other than CMYK process colors, such as RGB, orange, violet, photocyan, photomagenta, gray, and gold and silver. In order to increase the added value of the image, special color ink may be added depending on the application.

Next, gamma correction processing is performed (S103). In order to correct (adjust) the output variation of each color due to the difference between the aircraft and the medium, γ correction (one-dimensional input / output correction) is performed for each of the CMYK (+ spot colors).

Next, halftone processing is performed (S104). The image data up to this point has an amount of information of 8 bits (= 256 gradations) to 16 bits (65536 gradations) for each CMYK (+ spot color) color per pixel. On the other hand, the information of one pixel that can be expressed by the liquid discharge device 1 is insufficient because it is about 1 bit (2 values) of dot ON / OFF or 2 bits (4 values) of OFF / small / medium / large dots. It is necessary to replace the gradation information to be performed with the dot ratio within the unit area. The halftone process is a process of generating dot data by converting such a multi-value to a small value (about 2 to 4 values).

Next, the rendering process is performed (S105). Image recording (printing) is completed by ejecting ink droplets corresponding to the dot size from the nozzle of the liquid ejection head 31 (S106) based on the dot data after the halftone processing (S107). Here, rendering processing may be required depending on the configuration of the liquid discharge head 31. When "recording resolution = nozzle pitch", image recording can be performed by using the dot data after halftone processing as it is. However, when "recording resolution> nozzle pitch", it is necessary to perform multipath recording in which scanning is performed a plurality of times as described in FIGS. 3 and 4 in order to fill the difference in resolution. The rendering process is a process including a mask process for setting whether or not to drip each print pixel of a printed image printed by multipath recording based on the mask data described later.

FIG. 7 is a diagram showing an example of mask data. The mask data shown in FIG. 7 is used for mask processing in multi-pass recording of 2-pass 4-interrace, and is applied to the first mask data 51 applied to the first pass and the second pass. Includes the second mask data 52. The first and second mask data 51 and 52 have a one-to-one correspondence with usable nozzles, and indicate a threshold value indicating whether or not to allow droplets for each print pixel (dot) in a two-dimensional matrix (threshold matrix) format. It is a thing.

The first mask data 51 is data in which threshold values are arranged in a predetermined ascending order pattern on a matrix corresponding to print pixels. The ascending order pattern means the correspondence between the position of the frame on the matrix (the position of the print pixel) and the order in which the threshold value increases. The second mask data 52 is data arranged in a reverse ascending order pattern in which the threshold value is opposite to the ascending order pattern of the first mask data 51 on the matrix (common with the first mask data 51) corresponding to the print pixels. Is. In the present embodiment, a value of 1 to 100 (a value suggesting 1% to 100%) is used as the threshold value so that the drip ratio can be easily imagined, but the range of the threshold value is limited to this. It's not something. For example, it may be 1 to 255 according to the gradation.

FIG. 8 is a diagram showing a first example of setting mask data. Here, the drip permission ratio of the first pass is set to 50%, and the drip permission ratio of the second pass is set to 50%. In this way, by setting the threshold values 1 to 50 of both mask data 51 and 52 to allow droplets to be dropped, the ratio of pixels capable of dropping drops in the first pass and the second pass becomes a relationship of equal mutual complementation. .. Here, the description of "pixels capable of dripping" means that for dot data that does not require dripping, even if dripping is permitted in the mask data, nothing is finally recorded in the pixel. Because.

FIG. 9 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 8 and a final dropping permission range. As shown in FIG. 9, when the setting is as shown in FIG. 8, there is an equal mutual complementary relationship, and the final drop permission range is 100%.

FIG. 10 is a diagram showing a second example of setting mask data. Here, the drip permission ratio of the first pass is set to 60%, and the drip permission ratio of the second pass is set to 40%. Since the threshold value of the first mask data 51 and the threshold value of the second mask data 52 are arranged according to the ascending order patterns opposite to each other, in the case of a drop permission ratio of 100% in total as in this example, the result is It becomes an unequal mutual complementary relationship. In the example shown in FIG. 10, since the drop permission rate in the first pass is 60%, which is more than half, the number of pixels to be dropped first increases. Therefore, it is effective, for example, when using a medium that is easily deformed by heat. On the contrary, if the drop permission ratio of the first pass is made lower than 50%, the number of pixels to be dropped first is reduced. Therefore, it is effective, for example, when using a medium that does not easily absorb liquid.

FIG. 11 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 10 and a final dropping permission range. As shown in FIG. 11, when the setting is as shown in FIG. 10, an uneven mutual complementary relationship is formed, and the final drop permission range is 100%.

FIG. 12 is a diagram showing a third example of setting mask data. Here, the drip permission ratio of the first pass is set to 60%, and the drip permission ratio of the second pass is set to 60%. In such a case, 20% overstrikes occur at 40% to 60% positions. Here, the drip permission threshold is set in a continuous region of 1% to 60%, but if the drip permission threshold is set as follows, for example, it is possible to perform overstrike at different pixel positions for each color. ..
・ Cyan: 1% to 60% on the 1st pass → 1% to 60% on the 2nd pass → 40% to 60% where overstrikes occur
-Magenta: 1% to 50% for the first pass, 60% to 70%, 1% to 50% for the second pass, 60% to 70% → 60% to 70% where overstrikes occur
-Yellow: 1% to 50% in the first pass, 70% to 80%, 1% to 50% in the second pass, 70% to 80% → 70% to 80% where overstrikes occur
・ Black: 1% to 50% in the first pass, 80% to 90%, 1% to 50% in the second pass, 80% to 90% → 80% to 90% where overstrikes occur

In the case of a combination of colors that you do not want to actively overlap due to the characteristics of color development, such as cyan and magenta, and yellow and black, you can easily adjust so that the locations where overstrikes occur do not overlap by shifting the specified threshold range. It becomes possible to do.

FIG. 13 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 12 and a final dropping permission range. As shown in FIG. 13, when the setting is as shown in FIG. 12, overstrike occurs in the region where the threshold value is 40 to 60, and the final drop permission range is 120%.

FIG. 14 is a diagram showing a fourth example of setting mask data. Here, the drip permission ratio of the first pass is set to 40%, and the drip permission ratio of the second pass is set to 40%. In such a case, 20% decimation occurs.

FIG. 15 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 14 and a final dropping permission range. As shown in FIG. 15, when the setting is as shown in FIG. 14, thinning occurs in the region where the threshold value is 40 to 60, and the final drop permission range is 80%.

FIG. 16 is a diagram showing a first example of setting mask data when the main scanning path is divided into four. Here, the first mask data 51 is used as the mask data of the first pass and the second pass, and the second mask data 52 is used as the mask data of the third pass and the fourth pass (hereinafter, FIG. 23). Same as above). In addition, the drip permission ratio of the first pass is 1% to 25%, the drip permission ratio of the second pass is 25% to 50%, and the drip permission ratio of the third pass is 25% to 50%, and the drip permission ratio of the third pass is 25% to 50%. The drop permission ratio is set to 1% to 25%. In such a case, the 1st to 4th passes have an equal mutual complementary relationship.

FIG. 17 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 16 and a final dropping permission range. As shown in FIG. 17, when the settings are made as shown in FIG. 16, the first to fourth passes have a balanced mutual complementary relationship, and the final drop permission range is 100%.

FIG. 18 is a diagram showing a second example of setting mask data when the main scanning path is divided into four. Here, the drop permission ratio of the first pass is 1% to 10%, the drop permission ratio of the second pass is 11% to 30%, and the drop permission ratio of the third pass is 41% to 70%, 4 passes. The eye drop permission ratio is set to 1% to 40%. In such a case, the first to fourth passes have an imbalanced mutual complementary relationship.

FIG. 19 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 18 and a final dropping permission range. As shown in FIG. 19, when the settings are made as shown in FIG. 18, the first to fourth passes have an unbalanced mutual complementary relationship, and the final drop permission range is 100%.

FIG. 20 is a diagram showing a third example of setting mask data when the main scanning path is divided into four. Here, the first pass is 1% to 30%, the second pass is 25% to 55%, and the third pass is 20% to 50%, 4 passes. The eye drop permission ratio is set to 1% to 25% and 95% to 100%. In such a case, 20% of overstrikes occur in the first to fourth passes as a whole.

FIG. 21 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 20 and a final dropping permission range. As shown in FIG. 21, when the setting is as shown in FIG. 20, 20% of overstrikes occur, and the final drop permission range is 120%.

FIG. 22 is a diagram showing a fourth example of setting mask data when the main scanning path is divided into four. Here, the first pass is 1% to 20%, the second pass is 25% to 45%, and the third pass is 30% to 50%, 4 passes. The eye drop permission ratio is set to 5% to 25%. In such a case, 20% thinning occurs for the first to fourth passes as a whole.

FIG. 23 is a diagram showing an example of mask data corresponding to the dropping ratio shown in FIG. 22 and a final dropping permission range. As shown in FIG. 23, when the setting is as shown in FIG. 22, 20% thinning occurs, and the final drop permission range is 80%.

As described above, even in the case of 4 passes, it is possible to expand (or shrink) between each pass evenly or stepwise as in the case of 2 passes, and it is possible to set mutual complementation, overstrike and thinning. It is possible as well. In addition, when the number of passes is more than 2 passes, by shifting the start value of each threshold value of the ascending order pattern and the reverse ascending order pattern, it is possible to set the drip pixel separation, overstrike, thinning, etc. within the same ascending order pattern. Is possible. In addition, overstrike and thinning can coexist as long as the total does not exceed 100%.

FIG. 24 is a diagram showing an example of the correspondence between the FM mask data 61, the first mask data 51, and the second mask data 52 used in the halftone processing. The FM mask data 61 illustrated here is assigned a threshold value of 1 to 255 corresponding to the tone information (8 bits in this example) of the image data.

The ascending pattern of the first mask data 51 shown in FIG. 24 matches the ascending pattern of the FM mask data 61. Further, the ascending order pattern (reverse ascending order pattern) of the threshold value of the second mask data 52 has an opposite relationship to the ascending order pattern of the first mask data 51 and the FM mask data 61.

The FM mask data 61 used for the halftone processing is usually a mask pattern having high frequency characteristics having excellent dispersibility. Therefore, by making the ascending pattern of the threshold of the mask data used in the mask processing in the rendering correspond to the FM mask data 61, the drip pixel positions for each scan are dispersed as much as possible, and the influence of the landing position deviation is made inconspicuous. , It is possible to reduce the probability of adjacent landing within the same scan and reduce the occurrence of coalescence.

FIG. 25 shows an example of the dot generation result when rendering is performed by applying the first and second mask data 51 and 52 shown in FIG. 24. Here, the thick line frames in the first and second mask data 51 and 52 shown in FIG. 24 indicate the pixel positions where the overstrikes occur. In the case of the input gradation 64 of the highlight portion shown in FIG. 25, dot data is formed at a threshold value of 64 or less of the FM mask data 61. Since 64/255 ≈ 0.25, the dot droplet rate is about 25%. As described with reference to FIGS. 12 and 13, in the first and second mask data 51 and 52 of 120% overstrike, overstrike occurs in the region where the threshold value is 40 to 60, so that the ascending order patterns of the threshold values are aligned. In the FM mask data 61 and the first and second mask data 51 and 52, overstrike does not occur. Further, in the middle portion gradation in which the drip rate is 50% and the shadow portion gradation in which the drip rate is 78% or more, the region of the threshold value 40 to 60 in the first and second mask data 51 and 52 is included. Therefore, overstrikes will occur. In the highlight area where the dots are sparse and the landing position shift does not affect the image quality so much, the overstrikes often act in the direction of worsening the graininess. When the FM mask data 61 and the first and second mask data 51 and 52 can be synchronized as in the present embodiment, the pixels in which the overstrike occurs are set by the threshold values of the first and second mask data 51 and 52. Since it is possible to shift to the middle gradation region, it is possible to improve the unevenness resistance while suppressing the graininess.

Further, since the ascending order patterns of the threshold values of the first and second mask data 51 and 52 are opposite to each other, the occurrence of overstrike can be fixed in the middle gradation region. Overstrike occurs when the drop permission ratio of the first pass and the second pass exceeds 50%, but overstrike occurs from the threshold pixel of 50% to the upper and lower threshold pixels as the ratio is increased. Will continue to do. If the FM mask data 61 and the ascending order patterns of the threshold values of the first and second mask data 51 and 52 are aligned, the dots of the middle gradation are overstriked.

The control in the liquid discharge device 1 as described above is realized by a program that controls the CPU 11. The program may be provided pre-embedded in, for example, a ROM 12, NVRAM 14, or other auxiliary storage device. In addition, the program is a file in an installable format or an executable format, and is a CD-ROM (Compact Disc Read Only Memory), a flexible disc (FD), a CD-R (Compact Disk-Recordable), or a DVD (Digital Versatile Disc). It may be provided by recording on a recording medium that can be read by a computer such as. Further, the program may be stored on a computer connected to a network such as the Internet and provided by downloading via the network. The program may also be provided or distributed via a network such as the Internet.

In the above description, the case where the serial type inkjet head as shown in FIG. 2 is used as the liquid discharge head 31 has been described, but the configuration of the liquid discharge head 31 is not limited to this.

FIG. 26 is a diagram showing an example of the configuration of the liquid discharge head 201 according to the modified example. The liquid discharge head 201 illustrated here is a so-called line type inkjet head, and includes two line heads 211 and 212 in which a plurality of nozzles are arranged along the width direction (main scanning direction) of the medium. An image can be formed on the medium by displacing the relative positions of these line heads 211 and 212 and the medium in the sub-scanning direction. In such a liquid discharge head 201, “nozzle pitch” = “recording resolution in the main scanning direction”. Although omitted here, color printing can be performed by further providing a line head of another color (CMY or the like).

As described above, by providing the two line heads 211 and 212 of the same color, as shown in FIG. 26, recording can be performed with two nozzles for the same pixel. In the case of the liquid discharge head 201 having such a configuration, for example, the mask processing for one line head 211 is performed based on the first mask data 51, and the mask processing for the other line head 212 is performed for the second line head 212. This can be done based on the mask data 52.

According to the above embodiment, adjustment in multipath recording can be flexibly performed.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and the components in the above embodiments can be easily conceived by those skilled in the art and are substantially the same. , And so-called equal ranges are included. In addition, various omissions, substitutions, changes and combinations of components can be performed without departing from the gist of the above embodiment.

1 Liquid discharge device 11 CPU
12 ROM
13 RAM
14 NVRAM
18 External device connection I / F
19 Network I / F
20 Bus line 21 Paper carrier 22 Sub-scan driver 23 Main scan driver 30 Carriage 31 Liquid discharge head 32 Liquid discharge head driver 40 Operation panel 51 First mask data 52 Second mask data 61 FM mask data 101 Discharge unit 102 Operation Unit 103 Color processing unit 104 Halftone processing unit 105 Rendering unit 106 Discharge control unit 111 Mask processing unit 112 Setting unit 201 Liquid discharge head 211,212 Line head

Japanese Patent No. 6131216

Claims (9)

Based on the mask data, a mask processing unit that performs mask processing that sets whether or not to drop drops for each print pixel that constitutes a print image printed by multipath recording, and a mask processing unit.
Based on the result of the mask processing, the discharge control unit that controls the discharge unit that discharges the liquid and the discharge control unit
With
The mask data are arranged in a first mask data in which threshold values are arranged in a predetermined ascending order pattern on a matrix corresponding to the print pixels, and in a reverse ascending order pattern in which the threshold values are arranged in a reverse ascending order pattern opposite to the ascending order pattern on the matrix. Includes the second mask data
Liquid discharge device. A setting unit that enables setting the range of the threshold value that allows or prohibits dropping.
The liquid discharge device according to claim 1, further comprising. The setting unit enables settings related to mutual complementation in the multipath recording.
The liquid discharge device according to claim 2. The setting unit enables settings related to overstrike in the multipath recording.
The liquid discharge device according to claim 2 or 3. The setting unit enables settings related to thinning in the multipath recording.
The liquid discharge device according to any one of claims 2 to 4. A halftone processing unit that generates dot data indicating the necessity of dropping for each print pixel from image data.
The liquid discharge device according to any one of claims 1 to 5, further comprising. The halftone processing unit generates the dot data based on the FM mask data, and then generates the dot data.
The ascending order pattern and the reverse ascending order pattern correspond to the FM mask data.
The liquid discharge device according to claim 6. Based on the mask data, the process of performing mask processing to set whether or not to drop drops for each print pixel of the printed image printed by multipath recording, and
Based on the result of the mask processing, the process of controlling the discharge part that discharges the liquid and
Including
The mask data are arranged in a first mask data in which threshold values are arranged in a predetermined ascending order pattern on a matrix corresponding to the print pixels, and in a reverse ascending order pattern in which the threshold values are arranged in a reverse ascending order pattern opposite to the ascending order pattern on the matrix. Includes the second mask data
Image processing method. On the computer
Based on the mask data, mask processing that sets whether or not to drop drops for each print pixel of the print image printed by multipath recording, and
Based on the result of the mask processing, the process of controlling the discharge part that discharges the liquid and the process
To run,
The mask data are arranged in a first mask data in which threshold values are arranged in a predetermined ascending order pattern on a matrix corresponding to the print pixels, and in a reverse ascending order pattern in which the threshold values are arranged in a reverse ascending order pattern opposite to the ascending order pattern on the matrix. Includes the second mask data
program.

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