Printing device and computer program

Abstract

To suppress the variation in the density of a printed image.SOLUTION: A printer comprises: a print head which has a nozzle for discharging ink; a supply part which supplies the ink stored in a container to the print head; and a control part. The control part acquires information having the correlation with the height of a liquid level of the ink, acquires object image data, executes generation processing of generating the printing data on the basis of the object image data, and causes the print head to discharge the ink on the basis of the printing data. The printer includes adjustment processing of adjusting the printing data according to the information having the correlation with the height of the liquid level.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present specification relates to control of a print execution unit that includes a print head having nozzles for ejecting ink, and a supply unit that supplies ink stored in a container to the print head. [Background technology]

[0002] Patent Document 1 discloses an inkjet pen that prints images by ejecting ink from nozzles formed in an inkjet head. In this inkjet pen, an ink cartridge containing ink is disposed above the inkjet head, and ink is supplied from the ink cartridge to the inkjet head via a pipe. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 55-65560 Summary of the Invention [Problem to be solved by the invention]

[0004] In such inkjet printing devices, when the ink level in the ink cartridge fluctuates as ink is consumed, the head difference between the meniscus of the nozzle and the ink level in the ink cartridge fluctuates. If the amount of ink ejected from the nozzle fluctuates due to the head difference, the density of the image printed by the printing device may fluctuate.

[0005] This specification discloses a technique that can suppress fluctuations in an image printed by ejecting ink from a nozzle, which are caused by fluctuations in the water head difference. [Means for solving the problem]

[0006] The techniques disclosed in this specification can be implemented in the following application examples.

[0007] [Application Example 1] A printing device comprising: a print head having nozzles for ejecting ink; a supply unit that supplies ink contained in a container to the print head; and a control unit, wherein the control unit acquires information that correlates with the height of the liquid surface of the ink contained in the container, acquires target image data, executes a generation process that generates print data based on the target image data, and ejects ink from the print head based on the print data, and the generation process includes an adjustment process that adjusts the print data in accordance with the information.

[0008] According to the above configuration, the printing data is adjusted according to information that correlates with the height of the ink liquid surface, thereby suppressing fluctuations in the actual printed image due to the difference in head between the meniscus of the nozzle and the ink liquid surface in the container. [Application example 2] The printing device according to Application Example 1, the target image data is image data that indicates the color of each pixel using color values ​​in a first color system, the adjustment process is a color conversion process that converts color values ​​of the first color system into color values ​​of a second color system that includes a plurality of components corresponding to a plurality of types of ink used in printing, A printing device wherein the color conversion process is performed using a first color conversion profile when the height information indicates that the ink liquid level is a first height, and is performed using a second color conversion profile different from the first color conversion profile when the height information indicates that the ink liquid level is a second height different from the first height. [Application example 3] The printing device according to Application Example 1, the target image data is image data that indicates the color of each pixel using color values ​​in a first color system, the generation process includes a color conversion process that converts color values ​​of the first color system into color values ​​of a second color system that includes a plurality of components corresponding to a plurality of types of ink used in printing by the printing device, The printing device, wherein the adjustment process is a process of correcting color values ​​of the first color system in accordance with the information before the color conversion process. [Application example 4] The printing device according to Application Example 1, the target image data is image data that indicates the color of each pixel using color values ​​in a first color system, the generation process includes a color conversion process that converts color values ​​of the first color system into color values ​​of a second color system that includes a plurality of components corresponding to a plurality of types of ink used in printing by the printing device, The adjustment process is a process of correcting color values ​​of the second color system in accordance with the information after the color conversion process. [Application example 5] The printing device according to Application Example 1, the target image data is image data that indicates the color of each pixel using color values ​​of a second color system that includes multiple components corresponding to multiple types of ink used in printing by the printing device, the adjustment process is a halftone process that converts the target image data into dot data that indicates the dot formation state for each pixel, A printing device wherein the halftone processing is performed using first parameters when the height information indicates that the ink liquid level is a first height, and is performed using second parameters different from the first parameters when the height information indicates that the ink liquid level is a second height different from the first height. [Application Example 6] The printing device according to any one of Application Examples 1 to 5, the supply unit supplies a first color ink contained in a first container and a second color ink contained in a second container to the print head; the print head has first nozzles that eject the first color ink and second nozzles that eject the second color ink; the information includes first information correlated with the liquid level of the ink of the first color contained in the first container, and second information correlated with the liquid level of the ink of the second color contained in the second container, The adjustment process includes a process of adjusting data relating to the first color in the print data according to the first information, and a process of adjusting data relating to the second color in the print data according to the second information, and the adjustment process includes a process of adjusting data relating to the second color in the print data according to the second information, and the adjustment process includes a process of adjusting data relating to the second color in the print data according to the second information. [Application Example 7] The printing device according to any one of Application Examples 1 to 6, The container has a communication port that connects the inside and outside of the container. [Application Example 8] The printing device according to Application Example 7 further comprises: A printing device comprising a valve that switches between a communication state in which the inside and outside of the container are in communication with each other via the communication port, and a non-communication state in which the inside and outside of the container are not in communication with each other. [Application Example 9] The printing device according to Application Example 8, The control unit controls the valve to the non-communicating state while printing is being performed. [Application Example 10] The printing device according to Application Example 8, The control unit controls the valve to be in the communicating state while printing is being performed. [Application Example 11] The printing device according to any one of Application Examples 1 to 10, A printing device, wherein the adjustment process is a process of increasing the density of the image represented by the print data when the information indicates that the ink liquid level is a first level, compared to when the level information indicates that the ink liquid level is a second level that is higher than the first level. [Application Example 12] The printing device according to any one of Application Examples 1 to 11, The container is disposed at a position where the ink level is higher than the nozzle opening when the container contains a maximum amount of ink. [Application Example 13] The printing device according to any one of Application Examples 1 to 12, The printing device, wherein the information is a count value indicating the amount of ink used in printing.

[0009] The technology disclosed in this specification can be realized in various forms, such as multiple print data generation devices, print data generation methods, printing methods, computer programs for realizing the functions of these devices and methods, and recording media on which the computer programs are recorded. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a block diagram showing the configuration of a printer 200 according to the embodiment. [Figure 2]FIG. 2 is a diagram showing a schematic configuration of a print execution unit 100. [Figure 3] 10 is a flowchart of a printing process. [Figure 4] FIG. 10 is a diagram showing an example of a tone curve for correction processing. [Figure 5] 10 is a flowchart of a printing process according to a second embodiment. [Figure 6] 10 is a flowchart of an error diffusion process. [Figure 7] 10 is a flowchart of a printing process according to a third embodiment. [Figure 8] FIG. 4 is an explanatory diagram of selection of a color conversion profile. [Figure 9] 10 is a flowchart of a printing process according to a fourth embodiment. [Figure 10] FIG. 10 is a first diagram showing the configuration of an ink container according to a modified example. [Figure 11] FIG. 10 is a second diagram showing the configuration of the ink container of the modified example.

[0011] A. First Example: A-1: Printer 200 Configuration Next, the embodiment will be described based on an example. Fig. 1 is a block diagram showing the configuration of a printer 200 according to the example.

[0012] The printer 200 includes, for example, a print execution unit 100, a CPU 210 as a control device for the print execution unit 100, a non-volatile storage device 220 such as a hard disk drive or flash memory, a volatile storage device 230 such as RAM, an operation unit 260 such as buttons or a touch panel for acquiring user operations, a display unit 270 such as a liquid crystal display, and a communication unit 280. The printer 200 is connected to an external device, for example, a user terminal device 300, via the communication unit 280 so as to be able to communicate with the external device.

[0013] The volatile storage device 230 provides a buffer area 231 that temporarily stores various intermediate data generated when the CPU 210 performs processing. The non-volatile storage device 220 stores a computer program PG. In this embodiment, the computer program PG is a control program for controlling the printer 200. The computer program PG may be stored in the non-volatile storage device 220 when the printer 200 is shipped. Alternatively, the computer program PG may be provided in a form that is downloaded from a server or stored on a DVD-ROM or the like. The CPU 210 executes the computer program PG to perform processing for controlling the print execution unit 100, such as the printing processing described below.

[0014] The print execution unit 100 performs printing by ejecting each ink Ik of cyan (C), magenta (M), yellow (Y), and black (K). The print execution unit 100 includes a print head 110, a head drive unit 120, a main scanning unit 130, a transport unit 140, and an ink supply unit 150.

[0015] Figure 2 is a diagram showing a schematic configuration of the print execution unit 100. As shown in Figure 2(A), the main scanning unit 130 includes a carriage 133 that carries the print head 110, and a sliding shaft 134 that holds the carriage 133 so that it can move back and forth along the main scanning direction (the X-axis direction in Figure 2). The main scanning unit 130 uses the power of a main scanning motor (not shown) to move the carriage 133 back and forth along the sliding shaft 134. This achieves main scanning, which moves the print head 110 back and forth along the main scanning direction relative to the paper M.

[0016] The conveying section 140 holds the paper M and conveys the paper M in a conveying direction AR (the +Y direction in FIG. 2) that intersects with the main scanning direction. As shown in FIG. 2A, the conveying section 140 includes a paper tray 145, an upstream roller pair 142, and a downstream roller pair 141. Hereinafter, the upstream side (-Y side) of the conveying direction AR will also be simply referred to as the upstream side, and the downstream side (+Y side) of the conveying direction AR will also be simply referred to as the downstream side.

[0017] The upstream roller pair 142 holds the paper M upstream (-Y side) of the print head 110, and the downstream roller pair 141 holds the paper M downstream (+Y side) of the print head 110. The paper platform 145 is located between the upstream roller pair 142 and the downstream roller pair 141, and is positioned opposite the nozzle formation surface 111 of the print head 110. The downstream roller pair 141 and the upstream roller pair 142 are driven by a transport motor (not shown), thereby transporting the paper M.

[0018] The ink supply unit 150 includes, for each of the CMYK inks Ik, an ink container 151, an ink flow path 152, a valve mechanism 153, and a liquid level sensor 154. To avoid complication of the illustration, Fig. 2(A) only shows the ink container 151, ink flow path 152, valve mechanism 153, and liquid level sensor 154 for one color of ink Ik. In reality, these components 151 to 154 are lined up in the X direction for the four colors of ink Ik, CMYK.

[0019] Ink Ik is stored inside the ink container 151. The ink container 151 is mounted on the carriage 133 and is located above (on the +Z side of) the print head 110. For this reason, in this embodiment, the entire ink stored in the ink container 151 is located above the nozzle formation surface 111 of the print head 110.

[0020] An inlet OP1 for injecting ink Ik into the ink container 151 is formed on the top wall of the ink container 151. A lid 156 is normally attached to the inlet OP1 and is closed by the lid 156. When injecting the ink Ik, the lid 156 is removed and the ink Ik is injected from the bottle into the ink container 151 through the inlet OP1.

[0021] An air open port OP2 is formed in the upper part of the side wall of the ink container 151. The air open port OP2 penetrates the side wall of the ink container 151.

[0022] The valve mechanism 153 opens and closes the atmosphere open port OP2, for example, under the control of the CPU 210. When the atmosphere open port OP2 is open, the inside and outside of the ink container 151 are in communication with each other via the atmosphere open port OP2 (also referred to as a communication state). When the atmosphere open port OP2 is closed, the inside and outside of the ink container 151 are not in communication with each other (also referred to as a non-communication state). The valve mechanism 153 is, for example, a known electromagnetic valve including a valve 1531 and a solenoid 1532.

[0023] The solenoid 1532 is attached to the side wall of the ink container 151 via a support base 1533. The valve 1531 is supported by the solenoid 1532. The valve 1531 moves left and right (Y direction) as indicated by the arrow YM, for example, by the power generated by the solenoid 1532. For example, when no current is flowing through the solenoid 1532, the valve 1531 abuts against the atmosphere open port OP2 and closes the atmosphere open port OP2. For example, when current is flowing through the solenoid, the valve 1531 moves away from the atmosphere open port OP2 and opens the atmosphere open port OP2.

[0024] The liquid level sensor 154 is attached to the lower side of the side wall of the ink container 151. The liquid level sensor 154 detects whether the liquid level IS of the ink Ik in the ink container 151 is below a predetermined height, for example, under the control of the CPU 210. For example, the predetermined height is the height at which the liquid level sensor 154 is attached, and is a height corresponding to the remaining amount of ink Ik at which it is preferable to replenish the ink Ik (empty level or near-empty level). The liquid level sensor 154 may be a known sensor that measures, for example, the electrical resistance or light transmittance at a location at a predetermined height.

[0025] The ink flow path 152 is a flow path for supplying the ink Ik contained in the ink container 151 to the print head 110. The upper end of the ink flow path 152 communicates with the bottom surface of the ink container 151, and the lower end of the ink flow path 152 communicates with an internal flow path (not shown) of the print head 110.

[0026] It should be noted that some ink containers for printers are known to have a structure (for example, a structure using a porous body or a structure using a negative pressure valve) for maintaining the air pressure inside the container at a pressure (negative pressure) lower than atmospheric pressure. The ink container 151 of this embodiment does not have a structure for maintaining the pressure of the air layer Ar at a negative pressure.

[0027] Figure 2(B) shows the configuration of the print head 110 as seen from the -Z side (the bottom side in Figure 2). As shown in Figure 2(B), multiple nozzle rows consisting of multiple nozzles, i.e., nozzle rows NC, NM, NY, and NK that eject the above-mentioned C, M, Y, and K inks, are formed on the nozzle forming surface 111 of the print head 110. Each nozzle row includes multiple nozzles NZ lined up along the transport direction AR. The multiple nozzles NZ are positioned at different positions in the transport direction AR (+Y direction) and are lined up along the transport direction AR at a predetermined nozzle spacing NT.

[0028] The nozzle rows NC, NM, NY, and NK are positioned differently in the main scanning direction (X direction in FIG. 2B), and overlap each other in the transport direction AR (Y direction in FIG. 2B). For example, in the example of FIG. 2B, the nozzle row NM is arranged in the +X direction of the nozzle row NY, which ejects Y ink.

[0029] Each nozzle NZ opens in the nozzle forming surface 111. Therefore, the vertical position (position in the Z direction) of the opening of each nozzle NZ is the vertical position of the nozzle forming surface 111. An internal flow path (not shown) is formed for each nozzle NZ in the print head 110. An actuator (for example, a piezoelectric element) (not shown) is disposed in each internal flow path to deform the internal flow path and eject ink Ik from the nozzle NZ.

[0030] The head drive unit 120 (FIG. 1) supplies drive signals to each actuator of the print head 110 while the main scanning unit 130 is performing a main scan of the print head 110. This causes ink Ik to be ejected from each nozzle NZ of the print head 110 in accordance with the drive signals, and dots of the ink Ik are formed on the paper being transported by the transport unit 140.

[0031] Here, the difference between the height of the ink Ik liquid level IS in the ink container 151 and the height of the nozzle NZ opening is called the head difference ΔH (FIG. 2A). A convex or concave ink level called a meniscus is formed at the nozzle NZ opening. The pressure applied from above to the meniscus at the nozzle NZ opening includes head pressure and internal container air pressure. Head pressure is pressure caused by the weight of the ink Ik. Head pressure varies according to head difference ΔH, and increases as the head difference ΔH increases. Internal container air pressure is the air pressure of the air layer Ar above the ink level IS in the ink container 151. As printing is performed by the print execution unit 100 and the ink Ik is consumed, the ink level IS decreases. As the head difference ΔH decreases as the ink level IS decreases, the head pressure decreases as the ink level IS decreases.

[0032] The print execution unit 100 executes printing using the above-described components 110 to 150. That is, the print execution unit 100 prints an image on a print medium (e.g., paper) by alternately executing partial printing, in which the print head 110 forms dots on paper M while the main scanning unit 130 performs main scanning, and sub-scanning (transporting paper M) by the transport unit 140 multiple times.

[0033] A-2. Printing process The CPU 210 (FIG. 1) of the printer 200 executes printing processing based on, for example, a print instruction from a user input via the operation unit 260. The print instruction includes a specification of image data indicating the image to be printed. FIG. 3 is a flowchart of the printing processing.

[0034] In S100, the CPU 210 acquires count values ​​CV of ink consumption. The acquired count values ​​CV are four count values ​​CV that indicate the ink consumption amounts of the four CMYK color inks Ik. The count values ​​of the four CMYK color inks Ik are also expressed as count values ​​CVc, CVm, CVy, and CVk. These count values ​​CVm, CVy, and CVk are recorded, for example, in the non-volatile storage device 220. When there is no need to distinguish between these count values ​​CVm, CVy, and CVk, one count value is simply expressed as count value CV.

[0035] Each time printing is performed, the count value CV is increased by a value corresponding to the amount of ink consumed in that printing (S160, described below). The count value CV of a specific color (for example, C (cyan)) is reset when the ink container 151 for the specific color of ink Ik is refilled with the ink Ik. In this embodiment, when the user inputs via the operation unit 260 that the specific color of ink Ik has been refilled, it is determined that the specific color of ink Ik has been refilled. In this way, the count value CV is a value that indicates the amount of ink consumed after the ink container 151 was refilled with the ink Ik.

[0036] Here, if the amount of ink in the ink container 151 when refilled with ink Ik is Vmax, the remaining amount Vr of ink Ik in the ink container 151 can be expressed as (Vmax - CV). The height of the liquid surface IS of the ink Ik in the ink container 151 is uniquely determined by the remaining amount Vr of ink Ik in the ink container 151. For this reason, the count value CV of the ink consumption amount is information that correlates with the remaining amount Vr and the height of the liquid surface IS.

[0037] In S105, the CPU 210 acquires target image data. The target image data is image data used in the print process and is specified by a print instruction. The target image data is acquired from an external device or the volatile storage device 230. The target image data is image data having various formats, such as JPEG-compressed image data or image data described in a page description language.

[0038] In S110, the CPU 210 performs a rasterization process on the acquired target image data to generate RGB image data. The RGB image data is bitmap data that includes RGB values ​​for each pixel. The RGB values ​​are color values ​​in the RGB color system that include, for example, three component values ​​of red (R), green (G), and blue (B). The R, G, and B component values ​​are also referred to as the R value, G value, and B value, respectively.

[0039] In S115, the CPU 210 performs color conversion processing on the RGB image data. The color conversion processing is processing for converting the RGB values ​​of multiple pixels that make up the target raster line into CMYK values. The CMYK values ​​are color values ​​in the CMYK color system that include component values ​​(in this embodiment, C, M, Y, and K component values) that correspond to the inks used in printing. The color conversion processing is performed, for example, by referring to a known lookup table that defines the correspondence between RGB values ​​and CMYK values. The C, M, Y, and K component values ​​are also referred to as C values, M values, Y values, and K values, respectively. The color conversion processing generates CMYK image data that includes CMYK values ​​for each pixel.

[0040] In S120, the CPU 210 selects one target color from the four colors CMYK. In S125, the CPU 210 determines whether the count value CV of the target color is equal to or greater than a threshold value CVth. Here, the threshold value CVth is the count value CV when the height of the liquid level IS of the ink container 151 is equal to the reference height Hth (FIG. 2A). In other words, when the height of the liquid level IS of the ink container 151 is equal to Hth, the remaining amount Vrth of the ink Ik is (Vmax-CVth). As can be seen from the above explanation, determining whether the count value CV of the target color is equal to or greater than the threshold value CVth is equivalent to determining whether the height of the liquid level IS of the ink Ik of the target color is equal to or less than the reference height Hth.

[0041] If the count value CV of the target color is equal to or greater than the threshold value CVth (S125: YES), then in S130 the CPU 210 executes a correction process to increase the density of the target color component values. In other words, if it can be determined based on the count value CV that the height of the liquid surface IS of the target color ink Ik is equal to or less than the reference height Hth, the correction process is executed on the target color component values.

[0042] Fig. 4 is a diagram showing an example of a tone curve for correction processing. The tone curve TC in Fig. 4 defines the correspondence relationship between the input value Nin and the output value Nout for the range of values ​​that the component values ​​of the target color (for example, C value and M value) can take (256 gradation values ​​from 0 to 255 in this embodiment). The CPU 210 applies the tone curve TC in Fig. 4 to the component values ​​of the target color among the CMYK values ​​of each pixel included in the CMYK image data. With the tone curve TC in Fig. 4, the component values ​​after correction will be larger than the component values ​​before correction, except when the component values ​​are 0 or 255.

[0043] If the count value CV of the target color is less than the threshold value CVth (S125: NO), the CPU 210 skips S130. In other words, if it can be determined based on the count value CV that the height of the liquid surface IS of the target color ink Ik is higher than the reference height Hth, no correction process is performed on the component values ​​of the target color.

[0044] In S135, the CPU 210 determines whether all CMYK colors have been processed as the target color. If there are unprocessed colors (S135: NO), the CPU 210 returns to S120. If all colors have been processed (S135: YES), the CPU 210 proceeds to S140.

[0045] In S140, the CPU 210 performs halftone processing on the CMYK image data to generate dot data. The dot data is data that represents the dot formation state for each pixel for each of the CMYK color components. The value of each pixel in the dot data indicates the dot formation state in two gradations, for example, "no dot" and "dot present," or in four gradations, for example, "no dot," "small," "medium," and "large." The halftone processing is performed using known techniques such as dithering and error diffusion.

[0046] In S145, the CPU 210 controls the valve mechanism 153 provided in each of the CMYK ink containers 151 to open the air-open port OP2 of the ink container 151, which had been closed by the valve 1531. This allows communication between the inside and outside of each ink container 151, and the air pressure in the air layer Ar of each ink container 151 becomes atmospheric pressure.

[0047] In S150, the CPU 210 controls the valve mechanism 153 provided in each of the CMYK ink containers 151 to close the atmosphere open port OP2 opened in S145 with the valve 1531. This makes it possible to prevent, for example, the ink Ik from leaking from the atmosphere open port OP2 and foreign matter from entering the ink container 151 through the atmosphere open port OP2.

[0048] In S155, the CPU 210 outputs the print data to the print execution unit 100, causing the print execution unit 100 to execute printing. For example, the CPU 210 generates print data by rearranging the dot data in the order used for printing and adding control data such as print commands, and outputs the print data to the print execution unit 100. The print execution unit 100 prints an image on paper in accordance with the print data.

[0049] In S160, the CPU 210 updates each of the CMYK count values ​​CV recorded in the nonvolatile storage device 220. For example, the CPU 210 calculates the consumption amount of each of the CMYK inks Ik based on the print data, and adds the calculated value to each of the CMYK count values ​​CV. Once the count values ​​CV have been updated, the printing process ends.

[0050] According to the printing process of this embodiment described above, the CPU 210 acquires a count value CV, which is information correlated with the height of the liquid surface IS of the ink Ik contained in the ink container 151 (S100 in FIG. 3), acquires target image data (S105 in FIG. 3), executes a generation process to generate print data based on the target image data (S110-S140 in FIG. 3), and ejects ink from the print head 110 based on the print data (S155 in FIG. 3). The print data generation process includes an adjustment process (S120-S135 in FIG. 3) that adjusts the print data in accordance with the count value CV. As a result, the print data is adjusted in accordance with the count value CV, which correlates with the height of the liquid surface IS of the ink Ik, thereby suppressing variations in the actually printed image due to the head difference ΔH between the meniscus of the nozzle NZ and the liquid surface IS of the ink Ik in the ink container 151.

[0051] For example, since the density of the image indicated by the print data is adjusted according to the height of the liquid surface IS of the ink Ik, fluctuations in the density of the image actually printed due to the head difference ΔH between the meniscus of the nozzle NZ and the liquid surface of the ink Ik in the ink container 151 can be suppressed.

[0052] This will be explained in more detail. The smaller the pressure applied from above to the meniscus at the opening of the nozzle NZ, the more difficult it becomes for the ink Ik to be ejected from the nozzle NZ. For this reason, when the actuator is driven using the same drive signal, the smaller the pressure applied from above to the meniscus, the smaller the amount of ink Ik for one dot ejected from the nozzle NZ. When the amount of ink Ik for one dot decreases, the size (area) of each dot that forms the printed image decreases, and the density of the printed image decreases.

[0053] The lower the height of the ink level IS of the ink Ik, the smaller the head difference ΔH, and the smaller the pressure applied to the meniscus from above. Therefore, when the height of the ink level IS is equal to or less than the reference height Hth (FIG. 2A), the head difference ΔH is smaller than when the height of the ink level IS is higher than the reference height Hth (FIG. 2A). This reduces the area of ​​each dot forming the printed image, resulting in a lower density of the printed image. In this embodiment, when it is determined based on the count value CV that the height of the ink level IS is equal to or less than the reference height Hth (FIG. 2A) (YES in S125 of FIG. 3), a correction process is performed to increase the density of the target color in the image represented by the print data (hereinafter also referred to as the data density) (S130 of FIG. 3). As a result, increasing the data density offsets the decrease in density of the printed image caused by the smaller dot size, thereby suppressing a decrease in density of the actually printed image. Therefore, it is possible to prevent a difference in density between a printed image printed when the height of the liquid surface IS is equal to or less than the reference height Hth and a printed image printed when the height of the liquid surface IS is higher than the reference height Hth.

[0054] In this embodiment, the atmosphere open port OP2 is opened and closed (S145, S150) before printing, and the pressure inside the container is set to atmospheric pressure before printing. During printing, the atmosphere open port OP2 is closed, and as ink Ik is consumed during printing, the volume of the air layer Ar increases, and the pressure inside the container drops accordingly. However, unless the print volume in one printing process is excessively large, the impact of the drop in the pressure inside the container is thought to be small.

[0055] Furthermore, the adjustment process in the above embodiment is a process of correcting the CMYK values ​​using the count value CV (S120 to S135 in FIG. 3) after the color conversion process (S115 in FIG. 4). Because the component values ​​of the CMYK values ​​correspond to the four colors of ink Ik (CMYK) used in printing, it is easy to selectively correct the color of the ink Ik whose liquid level IS is equal to or lower than the reference height Hth. Therefore, the print data can be appropriately adjusted according to the height of the liquid level IS of the ink Ik.

[0056] Furthermore, in the above embodiment, print data is adjusted for each color of CMYK. That is, the ink information includes first information (e.g., cyan count value CVc) correlated with the height of the liquid level IS of a first color ink (e.g., cyan ink) and second information (e.g., magenta count value CVm) correlated with the height of the liquid level IS of a second color ink (e.g., magenta ink). The adjustment process includes a process of adjusting data related to the first color (e.g., cyan component value) of the print data in accordance with the first information, and a process of adjusting data related to the second color (e.g., magenta component value) of the print data in accordance with the second information (S120 to S135 in FIG. 3). The height of the liquid level IS of the ink container 151 differs for each color of CMYK depending on the consumption status of the ink Ik. In the above embodiment, density adjustment according to the height of the liquid level IS is performed for each color, thereby appropriately suppressing variations in density and color tone of images printed using multiple colors due to differences in the height of the liquid level IS of each ink Ik.

[0057] Furthermore, in the above embodiment, the ink container 151 has an atmosphere-opening port OP2 that connects the inside and outside of the ink container 151. As a result, by opening the atmosphere-opening port OP2, the air pressure inside the container can be set to atmospheric pressure, thereby reducing the effect of the air pressure inside the container on fluctuations in the pressure applied to the meniscus. As a result, the degree of density adjustment when generating print data can be easily determined by taking into account the head pressure caused by the head difference ΔH.

[0058] Furthermore, in the above embodiment, the print execution unit 100 includes a valve 1531 that switches between a connected state in which the inside and outside of the ink container 151 are connected via the atmosphere open port OP2, and a disconnected state in which the inside and outside of the ink container 151 are not connected. As a result, for example, by switching to the connected state, the pressure inside the container can be set to atmospheric pressure, and by switching to the disconnected state, ink leakage and intrusion of foreign matter from the atmosphere open port OP2 can be suppressed.

[0059] Furthermore, in the above embodiment, the CPU 210 controls the valve 1531 to be in a non-communicating state while printing is being performed (S150 in FIG. 3). As a result, for example, it is possible to prevent ink Ik from leaking from the open-air port OP2 while the ink container 151 is reciprocating in the main scanning direction due to main scanning during printing.

[0060] Furthermore, the adjustment process of this embodiment is a process for increasing the density of the image represented by the print data when the count value CV indicates that the height of the liquid level IS is a first height (specifically, a height equal to or less than the reference height Hth) compared to when the count value CV indicates that the height of the liquid level IS is a second height higher than the first height (specifically, a height higher than the reference height Hth) (see FIG. 4, etc.). As described above, the smaller the head difference ΔH, the smaller the amount of ink ejected, so the lower the height of the liquid level IS, the lower the density of the image actually printed. For this reason, it is preferable to increase the density of the image represented by the print data the lower the height of the liquid level IS, so this embodiment can suppress fluctuations in the density of the printed image.

[0061] Furthermore, in this embodiment, the ink container 151 is positioned so that the height of the liquid surface IS of the ink Ik is higher than the opening of the nozzle NZ (FIG. 2(A)). In this case, the head difference ΔH is likely to be large, and the density of the printed image is likely to fluctuate due to fluctuations in head pressure. In this embodiment, fluctuations in the density of the printed image can be suppressed when the density of the printed image is likely to fluctuate due to fluctuations in head pressure.

[0062] Furthermore, in this embodiment, the ink information used to determine the height of the liquid level IS is the count value CV, which indicates the amount of ink used in printing. As described above, the count value CV is information that correlates with the liquid level IS, and is a value that can be calculated with high accuracy based on the print data. Therefore, by using the count value CV as ink information, it is possible to appropriately perform adjustment processing according to the height of the liquid level IS.

[0063] B. Second Example Fig. 5 is a flowchart of the printing process of the second embodiment. In the second embodiment, the printing process of Fig. 5 is executed instead of the printing process of Fig. 3. Other configurations of the second embodiment are the same as those of the first embodiment.

[0064] The processes of S200 to S225 of the printing process in Fig. 5 are the same as S100 to S125 of Fig. 3. If the count value CV of the target color is equal to or greater than the threshold value CVth in S225 (S225: YES), then in S230 the CPU 210 sets the relative density value D used in the error diffusion process (described below) in S240 to a value Ds adjusted for adjusting the print data. If the count value CV of the target color is less than the threshold value CVth (S225: NO), then in S235 the CPU 210 sets the relative density value D used in the error diffusion process (described below) in S240 to a normal value Dn.

[0065] In other words, if it can be determined based on the count value CV that the height of the liquid surface IS of the ink Ik of the target color is equal to or less than the reference height Hth, the relative density value D is set to the adjusted value Ds, and if it can be determined that the height of the liquid surface IS of the ink Ik of the target color is higher than the reference height Hth, the relative density value D is set to the normal value Dn.

[0066] In S240, the CPU 210 performs error diffusion processing on the component values ​​of the target color in the CMYK image data to generate dot data of the target color.

[0067] 6 is a flowchart of the error diffusion process. In S300, the CPU 210 selects a pixel of interest. The CMYK image data represents an image in which a plurality of pixels are arranged in a matrix in the vertical and horizontal directions. The CPU 210 sequentially selects pixels of interest one pixel at a time along the horizontal direction, for example. After completing processing of one horizontally extending pixel line, the CPU 210 similarly selects pixels of interest one pixel at a time from another vertically adjacent pixel line.

[0068] In S310, the CPU 210 calculates an error value Et to be distributed to the pixel of interest. For a processed pixel, the error value Ea to be distributed from that pixel has already been calculated (S370, described later), and the error value Ea has been stored in an error buffer. The CPU 210 calculates the weighted sum of the error values ​​Ea distributed from the source pixels located around the pixel of interest as the error value Et. The source pixels and weights are specified, for example, by a known error matrix (not shown).

[0069] In S320, the CPU 210 calculates the corrected component value Na of the pixel of interest. The corrected component value Na is the sum of the component value Nin of the target color among the CMYK values ​​of the pixel of interest and the error value Et (Na=Nin+Et).

[0070] In S330, CPU 210 determines whether corrected component value Na is equal to or greater than a predetermined threshold value TH (e.g., 255). If corrected component value Na is equal to or greater than threshold value TH (S330: YES), then in S340 CPU 210 determines to form a dot for the pixel of interest. That is, the value of the pixel of interest in the dot data (also called the dot value) is set to a value indicating that a dot will be formed. If corrected component value Na is less than threshold value TH (S330: NO), then in S350 CPU 210 determines not to form a dot for the pixel of interest. That is, the dot value of the pixel of interest is set to a value indicating that a dot will not be formed.

[0071] In S360, the CPU 210 calculates an error value Ea to be distributed from the pixel of interest to other pixels. If the dot value of the pixel of interest is determined to be a value indicating that a dot is not to be formed, the error value Ea is the corrected component value Na (Ea = Na). If the dot value of the pixel of interest is determined to be a value indicating that a dot is to be formed, the error value Ea is the corrected component value Na minus the relative density value D (Ea = Na - D). Here, as described above, the relative density value D is the Ds or Dn determined for the color of interest in S230 or S235. As described above, the highly adjusted relative density value Ds is a value smaller than the normal relative density value Dn. For example, if the normal relative density value Dn is 255, the adjusted relative density value Ds is approximately 230 to 250. When the adjusted relative density value Ds is used, the error value Ea is larger than when the normal relative density value Dn is used. In S370, the CPU 210 stores the calculated error value Ea in the error buffer.

[0072] In S380, the CPU 210 determines whether all pixels in the CMYK image data have been processed as pixels of interest. If there are unprocessed pixels (S380: NO), the CPU 210 returns to S300. If all pixels have been processed (S380: YES), the CPU 210 ends the error diffusion process.

[0073] As can be seen from the above explanation, when the adjusted relative density value Ds is used, the error value Ea is larger than when the normal relative density value Dn is used, so the probability that dots will be formed for the target color increases, and the number of dots formed increases. Therefore, when the adjusted relative density value Ds is used, the density of the image represented by the print data can be made higher than when the normal relative density value Dn is used.

[0074] In S245 of Fig. 5 after the error diffusion process, the CPU 210 determines whether all of the CMYK colors have been processed as the target color, similar to S135 of Fig. 3. If there are unprocessed colors (S245: NO), the CPU 210 returns to S220. If all of the colors have been processed (S245: YES), the CPU 210 proceeds to S250. At this point, dot data has been generated for the four CMYK colors.

[0075] 3, in S250, the CPU 210 controls the valve mechanism 153 to open the air-open port OP2 of the ink container 151, which had been closed by the valve 1531. This allows communication between the inside and outside of each ink container 151, and the air pressure in the air layer Ar of each ink container 151 becomes atmospheric pressure.

[0076] In S255, similarly to S155 in FIG. 3, the CPU 210 outputs the print data to the print execution unit 100 and causes the print execution unit 100 to execute printing.

[0077] 3, in S260, the CPU 210 controls the valve mechanism 153 to close the atmosphere open port OP2 that was opened in S250 with the valve 1531. In the second embodiment, the atmosphere open port OP2 is closed after printing is performed, and therefore, unlike the first embodiment, printing is performed in a state in which the inside and outside of each ink container 151 are in communication with each other.

[0078] In S270, similarly to S160 in FIG. 3, the CPU 210 updates the count values ​​CV of CMYK recorded in the nonvolatile storage device 220, and ends the printing process.

[0079] According to the present embodiment described above, error diffusion processing is performed as halftone processing (S240 in FIG. 5). When the count value CV indicates that the height of the liquid level IS is a first height (specifically, a height equal to or less than the reference height Hth), the error diffusion processing is performed using a first parameter (specifically, an adjusted relative density value Ds). When the count value CV indicates that the height of the liquid level IS is a second height different from the first height (specifically, a height higher than the reference height Hth), the error diffusion processing is performed using a second parameter different from the first parameter (specifically, a normal relative density value Dn) (S225-S235 in FIG. 5). As a result, halftone processing is performed using different parameters depending on the height of the liquid level IS of the ink Ik, so the density of the image represented by the print data can be appropriately adjusted depending on the height of the liquid level IS of the ink Ik.

[0080] Specifically, as in the first embodiment, when the height of the liquid level IS is indicated as a first height (specifically, a height equal to or less than the reference height Hth), the density of the image represented by the print data can be increased compared to when the height of the liquid level IS is indicated as a second height higher than the first height (specifically, a height higher than the reference height Hth). Also, because halftone processing is performed for each color of CMYK ink Ik used in printing, it is easy to selectively correct the color of ink Ik for which the height of the liquid level IS is equal to or less than the reference height Hth.

[0081] Furthermore, according to this embodiment, unlike the first embodiment, the CPU 210 controls the valve 1531 to be in an open state while the print execution unit 100 is printing (S250 in FIG. 5). As a result, the air pressure inside the container is always maintained at atmospheric pressure during printing. As a result, the fluctuation in pressure applied to the meniscus only needs to be considered in terms of the head pressure caused by the head difference ΔH, making it easy to adjust the print data.

[0082] C. Third Example FIG. 7 is a flowchart of the printing process of the third embodiment. In the third embodiment, the printing process of FIG. 7 is executed instead of the printing process of FIG. 3. Other configurations of the third embodiment are the same as those of the first embodiment. In the flowchart of FIG. 7, the same processes as those in the flowchart of FIG. 3 are assigned the same reference numerals as in FIG. 3, and processes different from those in the flowchart of FIG. 3 are assigned the suffix "C".

[0083] The processing of S100 to S110 in Fig. 7 is the same as S100 to S110 in Fig. 3. In S120C in Fig. 7 after S110, the CPU 210 determines whether or not there is one or more colors of ink Ik of the four colors of CMYK whose count value CV is equal to or greater than the threshold value TH.

[0084] If there is no color of ink Ik whose count value CV is equal to or greater than the threshold value TH (S120C: NO), then in S130C of Fig. 7, the CPU 210 selects a normal color conversion profile. The normal color conversion profile is the same as the color conversion profile used in the color conversion process of the first embodiment (S115 of Fig. 3). In other words, if the height of the liquid level IS of all ink containers 151 is higher than the reference height Hth, the normal color conversion profile (also called the normal profile) is selected.

[0085] If there is one or more colors of ink Ik whose count value CV is equal to or greater than the threshold value TH (S120C: YES), then in S125C of FIG. 7, the CPU 210 selects a color conversion profile (also called an adjustment profile) that has been adjusted to adjust the density. The adjustment profile is a lookup table similar to the normal profile. The adjustment profile converts at least some RGB values ​​into CMYK values ​​that indicate colors with a higher density than when the normal profile is used. In other words, if the height of the liquid level IS of at least one ink container 151 is equal to or less than the reference height Hth, the adjustment profile is selected.

[0086] FIG. 8 is an explanatory diagram of the selection of a color conversion profile. As shown in FIG. 8, there is only one normal profile, but 15 adjustment profiles are prepared. These 16 color conversion profiles are created in advance and stored in the non-volatile storage device 220 along with the computer program PG. FIG. 8 shows all combinations (16 combinations) when the four CMYK inks Ik are in either a "high" or "low" state. For example, when C ink is "high," this means that the height of the C ink liquid surface IS is higher than the reference height Hth, and when C ink is "low," this means that the height of the C ink liquid surface IS is equal to or lower than the reference height. The 16 color conversion profiles are associated with one of the 16 combinations.

[0087] In S125C of FIG. 7, one profile is selected from 15 adjustment profiles depending on whether the four ink colors Ik are in a "high" or "low" state. For example, if the C ink is in a "low" state and the three ink colors Ik (MYK) are in a "high" state, adjustment profile 1 is selected. Adjustment profile 1 converts, among all RGB values, RGB values ​​that indicate a color printed using the C ink into CMYK values ​​that indicate a color with a higher density than when a normal color conversion profile is used. Adjustment profile 1 converts, among all RGB values, RGB values ​​that indicate a color printed without the C ink into CMYK values ​​that indicate the same color as when a normal color conversion profile is used. Furthermore, if the two ink colors MY are in a "low" state and the two ink colors CK are in a "high" state, adjustment profile 8 is selected. Adjustment profile 8 converts, among all RGB values, RGB values ​​that indicate a color printed using at least one of the two ink colors MY into CMYK values ​​that indicate a color with a higher density than when a normal color conversion profile is used. The adjustment profile 8 converts, of all RGB values, RGB values ​​that indicate colors that are printed without using the two MY ink colors into CMYK values ​​that indicate the same colors as when a normal color conversion profile is used.

[0088] 7, CPU 210 executes color conversion processing using the color conversion profile selected in S125C or S130C, thereby converting RGB image data into CMYK image data.

[0089] The processes of S140 to S160 in FIG. 7 are the same as those of S140 to S160 in FIG.

[0090] According to the present embodiment described above, the color conversion process is performed using a first color conversion profile (specifically, an adjustment profile) when the count value CV indicates that the height of the liquid level IS is a first height (specifically, a height equal to or less than the reference height Hth), and is performed using a second color conversion profile (specifically, a normal profile) different from the first color conversion profile when the count value CV indicates that the height of the liquid level IS is a second height different from the first height (specifically, a height higher than the reference height Hth) (S120C to 130C in FIG. 7). As a result, the color conversion process is performed using a different color conversion profile depending on the height of the liquid level IS of the ink Ik, so the density of the image represented by the print data can be appropriately adjusted depending on the height of the liquid level IS of the ink Ik.

[0091] Furthermore, in the above embodiment, one adjustment profile is selected from a plurality of adjustment profiles prepared for each combination pattern of inks Ik whose liquid surface IS heights are equal to or less than the reference height Hth (FIG. 8). As a result, it is possible to selectively correct the color of the ink Ik whose liquid surface IS heights are equal to or less than the reference height Hth.

[0092] D. Fourth Example Fig. 9 is a flowchart of the printing process of the fourth embodiment. In the fourth embodiment, the printing process of Fig. 9 is executed instead of the printing process of Fig. 3. Other configurations of the fourth embodiment are the same as those of the first embodiment. In the flowchart of Fig. 9, the same processes as those in the flowchart of Fig. 3 are assigned the same reference numerals as in Fig. 3, and processes different from those in the flowchart of Fig. 3 are assigned the suffix "D" to the reference numerals.

[0093] The processes of S100 to S110 in Fig. 9 are the same as S100 to S110 in Fig. 3. In S115D in Fig. 9 after S110, the CPU 210 determines whether or not there is one or more colors of ink Ik of the four colors of CMYK whose count value CV is equal to or greater than the threshold value TH.

[0094] If there is one or more colors of ink Ik whose count value CV is equal to or greater than the threshold value TH (S115D: YES), then in S120D of FIG. 9, the CPU 210 selects a correction profile. A correction profile is a profile that defines the correspondence between RGB values ​​before correction and RGB values ​​after correction, and is, for example, a lookup table. The correction profile converts at least some of the RGB values ​​into RGB values ​​that indicate a higher density color. In other words, if the height of the liquid level IS of at least one ink container 151 is equal to or less than the reference height Hth, the correction profile is selected.

[0095] Similar to the adjustment profiles in the third embodiment (FIG. 8), 15 correction profiles are prepared for each combination of the four CMYK inks Ik, assuming that they are either "high" or "low." These 15 correction profiles are created in advance and stored in the non-volatile storage device 220 along with the computer program PG. In step S120D of FIG. 9, one of the 15 correction profiles is selected depending on whether the four inks Ik are "high" or "low." For example, if the C ink is "low" and the three MYK inks Ik are "high," a profile is selected that converts, of all RGB values, the RGB values ​​representing the color printed using the C ink into RGB values ​​representing a more dense color. Furthermore, if the two MY inks Ik are "low" and the two CK inks Ik are "high," a profile is selected that converts, of all RGB values, the RGB values ​​representing the color printed using at least one of the two MY inks into RGB values ​​representing a more dense color.

[0096] In S130D of FIG. 9, the CPU 210 corrects the RGB values ​​of each pixel of the RGB image data using the correction profile selected in S120D.

[0097] If there is no color of ink Ik whose count value CV is equal to or greater than the threshold value TH (S115D: NO), S120D and S130D in Fig. 9 are skipped. In other words, if it is determined that the height of the liquid surface IS of all inks Ik is higher than the reference height Hth, no correction is performed on the RGB image data.

[0098] In S135D of Fig. 9, the CPU 210 performs color conversion processing on the RGB image data, similar to S115 of Fig. 3. As a result, the RGB image data is converted into CMYK image data.

[0099] The processes of S140 to S160 in FIG. 9 are the same as those of S140 to S160 in FIG.

[0100] According to the present embodiment described above, the adjustment process according to the height of the liquid surface IS is a process of correcting the color values ​​(RGB values) in the RGB color system using the count value CV (S115D to S130D in FIG. 9) before the color conversion process (S135D in FIG. 9). As a result, the color values ​​in the RGB color system are corrected using the count value CV, so the density of the image represented by the print data can be appropriately adjusted according to the height of the ink liquid surface.

[0101] Furthermore, in the above embodiment, as in the third embodiment, one correction profile is selected from a plurality of correction profiles prepared for each combination pattern of inks Ik whose liquid surface IS heights are equal to or less than the reference height Hth (FIG. 8). As a result, it is possible to selectively correct the color of the ink Ik whose liquid surface IS heights are equal to or less than the reference height Hth.

[0102] E. Variations (1) Figure 10 is a first diagram showing the configuration of an ink container in a modified example. In the above embodiments, the ink container 151 is mounted on the carriage 133, but this is not limited to this. The ink container 151A in Figure 10 is not mounted on the carriage 133, but is installed in a predetermined position on the housing of the printer 200, for example. The ink container 151A in Figure 10 and the print head 110 are connected via an ink flow path 152A. Ink Ik in the ink container 151A is supplied to the print head 110 via the ink flow path 152A.

[0103] 2A, the ink container 151A is formed with an inlet OP1A and an open-to-air port OP2A, and is equipped with a liquid level sensor 154A. A removable lid 156A is attached to the inlet OP1A, similar to the inlet OP1 of the ink container 151 in FIG.

[0104] 10, the ink container 151A does not have a valve mechanism attached to the portion where the atmosphere open port OP2 is formed. In this way, the valve mechanism that opens and closes the atmosphere open port may be omitted. In this case, the inside and outside of the ink container 151A are always in communication with each other.

[0105] 10 is positioned above the openings of the nozzles NZ of the print head 110. Therefore, the height of the liquid surface IS in the ink container 151A is always higher than the openings of the nozzles NZ.

[0106] (2) Figure 11 is a second diagram showing the configuration of a modified ink container. In each of the above embodiments, the print execution unit 100 includes only one ink container 151, but this is not limited to this. In the modified example of Figure 11, the print execution unit includes two ink containers 151B and 151C.

[0107] The ink container 151B is mounted on the carriage 133. The ink container 151B and the print head 110 are connected via an ink flow path 152B. The ink Ik in the ink container 151B is supplied to the print head 110 via the ink flow path 152B.

[0108] The ink container 151C is not mounted on the carriage 133, but is installed, for example, at a predetermined position on the housing of the printer 200. The ink container 151C and the ink container 151B are connected via an ink flow path 152C. The ink Ik in the ink container 151C is supplied to the ink container 151B via the ink flow path 152C.

[0109] An air open port OP2B is formed in the ink container 151B, and an air open port OP2C is formed in the ink container 151C. Therefore, the internal pressure of the ink container 151B and the internal pressure of the ink container 151C are both atmospheric pressure. As a result, the liquid level ISB of the ink Ik in the ink container 151B and the liquid level ISC of the ink Ik in the ink container 151C are at the same height.

[0110] 2A, the ink container 151C is formed with an inlet OP1C and is equipped with a liquid level sensor 154C. A removable lid 156C is attached to the inlet OP1B, similar to the inlet OP1 of the ink container 151 in FIG.

[0111] No valve mechanism is attached to the portions of the ink containers 151B and 151C where the open-air ports OP2B and OP2C are formed, so that the inside and outside of the ink containers 151A and 151C are always in communication with each other.

[0112] The entire ink container 151B and the entire ink container 151C are positioned above the openings of the nozzles NZ of the print head 110. Therefore, the heights of the liquid levels ISA and ISB of the ink containers 151B and 151C are always higher than the openings of the nozzles NZ.

[0113] (3) In the above embodiments, the ink information is the count value CV of the ink consumption amount, but is not limited to this. The ink information may be, for example, information indicating the remaining amount of ink in the ink container 151. Information indicating the remaining amount of ink can be easily calculated using, for example, the count value CV.

[0114] The ink information may also be, for example, the detection result obtained using a liquid level sensor. For example, a liquid level sensor similar to the liquid level sensor 154 in Fig. 2A may be attached at the position of the reference height Hth in Fig. 2A. Then, the detection result of the liquid level sensor may be used to determine whether the liquid level IS is equal to or lower than the reference height Hth.

[0115] (4) In the above embodiments, the adjustment process involves increasing the density of the image data represented by the print data. However, this is not limiting. For example, an adjustment process may be performed to adjust the hue of the image data without changing the density. For example, if the liquid level IS of the C ink Ik is equal to or lower than the reference height Hth and the liquid level IS of the MYK ink Ik is higher than the reference height Hth, the C dots in the printed image may be smaller than the MYK dots, potentially causing a change in the hue of the printed image. For this reason, the adjustment process may involve adjusting the hue of the image represented by the print data to offset the change in hue of the printed image.

[0116] (5) In the above embodiments, the density adjustment according to the height of the ink liquid level is performed in two stages: when the liquid level IS is equal to or less than the reference height Hth (adjusted), and when the liquid level IS is higher than the reference height Hth (no adjustment). This is not limiting, and multiple stages of adjustment, such as three or more stages, may be performed. For example, when the liquid level IS is higher than the reference height Hth1, an adjustment to decrease the density is performed; when the liquid level IS is equal to or less than the reference height Hth1 and higher than the reference height Hth2, no adjustment to the density is performed; and when the liquid level IS is lower than the reference height Hth2, an adjustment to increase the density is performed.

[0117] (6) In each of the above embodiments, the count value CV is acquired only once for each printing process, i.e., each print job, and a determination is made as to whether or not to adjust the density. This is not a limitation; the count value CV may be acquired, for example, each time n pages (n is an integer greater than or equal to 1) are printed, or each time n partial prints (passes) are performed. Then, each time the count value CV is acquired, a determination is made as to whether or not to adjust the density.

[0118] (7) In the second embodiment (FIGS. 5 and 6), error diffusion processing is performed as halftone processing, and the parameter used in the error diffusion processing depending on the height of the liquid level IS is a relative density value. Alternatively, dither processing may be performed as halftone processing. In this case, the parameter used in the error diffusion processing depending on the height of the liquid level IS is a threshold value defined in a dither matrix. For example, when the liquid level IS is equal to or less than the reference height Hth, a dither matrix with a smaller threshold value is used compared to when the liquid level IS is higher than the reference height Hth. Even in this case, as in the second embodiment, when the liquid level IS is equal to or less than the reference height Hth, the density of the image data represented by the print data can be increased compared to when the liquid level IS is higher than the reference height Hth.

[0119] (8) In the above embodiment, the printing unit 100 prints using four colors of ink Ik: CMYK. However, the printing unit may be configured to print using only K ink Ik, or may be configured to print using three colors of ink Ik: CMY, or may be configured to print using five or more colors of ink Ik. In any case, it is preferable to determine whether the height of the liquid surface IS for each ink Ik is equal to or less than the reference Hth, and to adjust the color density of that ink Ik based on the determination result.

[0120] (9) In the above-described embodiments and modifications, the entire ink Ik in the ink container 151 is located higher than the opening of the nozzle NZ (FIGS. 2A, 10, and 11). Alternatively, the entire or part of the ink Ik in the ink container may be located lower than the opening of the nozzle NZ.

[0121] However, it is preferable that the ink container is placed in a position where the height of the liquid surface IS of the ink Ik is at least higher than the opening of the nozzle NZ when the maximum amount of ink Ik is contained in the ink container 151. In this case, the head difference ΔH will have a large effect on the fluctuation in the ejection amount of the ink Ik, so it is very important to adjust the concentration according to the height of the liquid surface IS.

[0122] (10) In each of the above embodiments, the ink container 151 is fixed to the carriage 133, and is replenished with ink by injecting ink through the inlet OP1. Alternatively, the ink container 151 may be configured to be detachable from the carriage 133. In this case, the ink Ik is replenished by replacing the ink container, whose ink Ik has been used, with a new ink container containing the ink Ik.

[0123] (11) The print execution unit 100 may be a so-called line printer. For example, the print execution unit may not have a main scanning unit 130, and the print head 110 may have a nozzle group for each color, consisting of multiple nozzles aligned in a direction perpendicular to the transport direction (also called a line head). The multiple nozzles in each nozzle group are aligned over a length roughly equal to the width of the paper. A line printer prints without performing main scanning.

[0124] (12) The printing process of each embodiment may be executed by a CPU of a terminal device (e.g., a user's smartphone or personal computer) connected to the printer, instead of the CPU 210 of the printer 200. In this case, the CPU of the terminal device functions as a printer driver by executing a computer program provided by the printer manufacturer, for example. The CPU of the terminal device then executes the printing process of each embodiment as the printer driver. In this case, the CPU of the terminal device obtains ink information, such as the count value CV, from the printer by querying the printer.

[0125] Furthermore, the device that executes the printing process of each embodiment may be, for example, a server that acquires image data from a printer or a terminal device and generates print data using the image data. Such a server may be a plurality of computers (so-called cloud servers) that can communicate with each other via a network.

[0126] (13) In each of the above embodiments, some of the hardware components may be replaced with software, and conversely, some or all of the software components may be replaced with hardware. For example, when the printing process of FIG. 3 is executed by printer 200, halftone processing and color conversion processing may be implemented by a dedicated hardware circuit (e.g., ASIC) that operates according to instructions from CPU 210 of printer 200.

[0127] The present invention has been described above based on examples and modifications, but the above-described embodiments of the invention are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are also included in the present invention. [Explanation of symbols]

[0128] 100...print execution unit, 110...print head, 110...component, 111...nozzle formation surface, 120...head drive unit, 130...main scanning unit, 133...carriage, 134...sliding shaft, 140...conveyance unit, 141...downstream roller pair, 142...upstream roller pair, 145...paper stand, 150...ink supply unit, 151...ink container, 151...component, 151, 151A to 151C...ink container, 152, 152A to 152C...ink flow path, 153...valve mechanism, 1531...valve, 154...liquid level sensor, 154A, 154C... Liquid level sensor, 156, 156A, 156C...lid, 200...printer, 210...CPU, 220...nonvolatile storage device, 230...volatile storage device, 231...buffer area, 260...operation unit, 270...display unit, 280...communication unit, 300...terminal device, 310...CPU, Ar...air layer, CV...count value, Dn, Ds...relative concentration value, Ik...ink, M...paper, NZ...nozzle, OP1, OP1A to OP1C...injection port, OP2, OP2A to OP2C...atmospheric opening port, PG...computer program, TC...tone curve

Claims

1. a print head having nozzles for ejecting ink; a supply unit that supplies ink contained in a container to the print head; A control unit; Equipped with The control unit acquiring height information indicating the height of the liquid surface of the ink contained in the container relative to the opening of the nozzle; obtaining comparison information determined by comparing the height information with threshold information indicating a reference height of the liquid level relative to the opening; Acquire target image data; execute a generation process for generating print data based on the target image data; ejecting ink from the print head based on the print data; The generating process includes an adjusting process for adjusting the print data in accordance with the comparison information.

2. 2. The printing device according to claim 1, the target image data is image data that indicates a color for each pixel using a color value in a first color system, the adjustment process is a color conversion process that converts color values ​​of the first color system into color values ​​of a second color system that includes a plurality of components corresponding to a plurality of types of ink used in printing, A printing device wherein the color conversion process is performed using a first color conversion profile when the comparison information indicates that the ink liquid level is below the reference height, and is performed using a second color conversion profile different from the first color conversion profile when the comparison information indicates that the ink liquid level is higher than the reference height.

3. 2. The printing device according to claim 1, the target image data is image data that indicates a color for each pixel using a color value in a first color system, the generation process includes a color conversion process of converting color values ​​of the first color system into color values ​​of a second color system that includes a plurality of components corresponding to a plurality of types of ink used in printing by the printing device, The adjustment process is a process of correcting color values ​​of the first color system in accordance with the comparison information before the color conversion process.

4. 2. The printing device according to claim 1, the target image data is image data that indicates a color for each pixel using a color value in a first color system, the generation process includes a color conversion process of converting color values ​​of the first color system into color values ​​of a second color system that includes a plurality of components corresponding to a plurality of types of ink used in printing by the printing device, The adjustment process is a process of correcting color values ​​of the second color system in accordance with the comparison information after the color conversion process.

5. 2. The printing device according to claim 1, the target image data is image data that indicates the color of each pixel using color values ​​of a second color system that includes a plurality of components corresponding to a plurality of types of ink used in printing by the printing device, the adjustment process is a halftone process that converts the target image data into dot data that indicates the dot formation state for each pixel, A printing device wherein the halftone processing is performed using first parameters when the comparison information indicates that the ink level is equal to or lower than the reference height, and is performed using second parameters different from the first parameters when the comparison information indicates that the ink level is higher than the reference height.

6. The printing device according to any one of claims 1 to 5, the supply unit supplies a first color ink contained in a first container and a second color ink contained in a second container to the print head; the print head has a first nozzle that ejects the first color ink and a second nozzle that ejects the second color ink; the height information includes first height information indicating a liquid level of the ink of the first color contained in the first container, and second height information indicating a liquid level of the ink of the second color contained in the second container, the comparison information includes first comparison information determined by comparing the first height information with the threshold information, and second comparison information determined by comparing the second height information with the threshold information; The adjustment process includes a process of adjusting data relating to the first color in the printing data in accordance with the height of the ink surface of the first color in accordance with the first comparison information, and a process of adjusting data relating to the second color in the printing data in accordance with the height of the ink surface of the second color in accordance with the second comparison information.

7. The printing device according to any one of claims 1 to 6, The container has a communication port that connects the inside and outside of the container.

8. 8. The printing device according to claim 7, further comprising: A printing device comprising a valve that switches between a communication state in which the inside and outside of the container are in communication with each other via the communication port, and a non-communication state in which the inside and outside of the container are not in communication with each other.

9. 9. The printing device according to claim 8, The control unit controls the valve to the non-communicating state while printing is being performed.

10. 9. The printing device according to claim 8, The control unit controls the valve to be in the communicating state while printing is being performed.

11. The printing device according to any one of claims 1 to 10, A printing device in which the adjustment process is a process of increasing the density of the image represented by the print data when the comparison information indicates that the ink level is below the reference height, compared to when the comparison information indicates that the ink level is higher than the reference height.

12. The printing device according to any one of claims 1 to 11, The container is disposed at a position where the ink level is higher than the nozzle opening when the container contains a maximum amount of ink.

13. The printing device according to any one of claims 1 to 12, A printing device, wherein the height information is a count value indicating the amount of ink used in printing.

14. A computer program for controlling a printing device including a print head having nozzles for ejecting ink, and a supply unit that supplies ink stored in a container to the print head, the computer program comprising: acquiring height information indicating a height of a liquid surface of the ink contained in the container relative to an opening of the nozzle; obtaining comparison information determined by comparing the height information with threshold information indicating a reference height of the liquid level relative to the opening; acquiring target image data; Executing a generation process to generate print data based on the target image data; This is realized by a computer, The generating process includes an adjusting process for adjusting the print data in accordance with the comparison information.

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