Recording system

Abstract

To solve the problem that a surface of a medium is sometimes insufficiently filled due to shortage of discharged liquid corresponding to a neighboring color of a darkest part.SOLUTION: A recording system includes a recording head having a plurality of nozzles that can discharge liquid to a medium and a control part that controls the recording head. The control part controls discharging of the liquid by the recording head, on the basis of total amounts of the discharged liquid corresponding to a color in input data, and performs control by which the total discharge amounts of the liquid at peak is discharged, when a predetermined color belonging to a first range in a color space in the input data is inputted as the color in the input data, where the total discharge amounts of the liquid in peak are larger than the total discharge amounts thereof corresponding to the darkest part in the color space. When the darkest part is defined as 0 and the brightest part in the color space is defined as 1, the first range is a range of 1 / 25.5 or below except for the darkest part.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a recording system that controls a recording head capable of discharging a liquid.

Background Art

[0002] In a recording apparatus or system that discharges and records a liquid such as ink, color conversion processing is performed to convert input data expressed in a certain color space into the discharge amount for each color of ink that the recording head can discharge.

[0003] As a related technique, a color conversion table used by a color conversion unit in a color mode, which is a table showing the driving amount of CMYK colored inks with respect to an input signal value RGB, is disclosed (see FIG. 24(a) of Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When the input signal value corresponding to the peak of the combined driving amount of CMYK is separated from the input signal = 0, which is the darkest part, by a certain degree as in the conventional color conversion table, the driving amount corresponding to the color in the vicinity of the darkest part tends to be insufficient, and in the recording result, the filling of the paper surface of this neighboring color is poor and the image quality tends to deteriorate.

Means for Solving the Problems

[0006] The recording system includes a recording head having a plurality of nozzles capable of discharging liquid onto a medium, and a control unit that controls the recording head, wherein the control unit controls the discharging of the liquid by the recording head based on the total amount of liquid discharging corresponding to the color of the input data, and when a predetermined color belonging to a first range in the color space of the input data is input as the color of the input data, the control unit controls the discharging of the peak total amount of liquid, the peak total amount of liquid discharging is greater than the total amount of liquid discharging corresponding to the darkest part of the color space, and the first range is a range of 1 / 25.5 or less excluding the darkest part, with the darkest part being 0 and the brightest part of the color space being 1. [Brief explanation of the drawing]

[0007] [Figure 1] A block diagram illustrating the system configuration of this embodiment in a simplified manner. [Figure 2] A simplified diagram showing the relationship between the media and the recording head from a top-down perspective. [Figure 3] A flowchart illustrating the recording control process. [Figure 4] A diagram showing a simplified representation of a part of the color conversion LUT of this embodiment in the RGB color space. [Figure 5] Figures 5A and 5B show color conversion LUTs as comparative examples, respectively. [Figure 6] Figure 6A shows a color conversion LUT as a comparative example, and Figure 6B shows an example of a color conversion LUT according to this embodiment. [Figure 7] A flowchart illustrating an example of a grid point position change process. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below with reference to the figures. Note that the figures are merely illustrative examples for illustrating these embodiments. Because the figures are illustrative, their proportions and shapes may not be accurate, they may not be consistent with each other, or some parts may be omitted.

[0009] 1. Outline of the device configuration: Figure 1 shows a simplified configuration of the recording system 10 according to this embodiment. The recording method is performed by the recording system 10. The recording system 10 includes a control unit 11, a display unit 13, an operation reception unit 14, a storage unit 15, a communication IF 16, a transport unit 17, a carriage 18, a recording head 19, etc. IF stands for interface. The control unit 11 is composed of one or more ICs having a CPU 11a as a processor, ROM 11b, RAM 11c, etc., and other non-volatile memory, etc.

[0010] In the control unit 11, the processor, i.e., the CPU 11a, performs calculation processing according to the program 12 stored in the ROM 11b or other memory, using the RAM 11c or the like as a work area, thereby realizing various functions such as the recording data generation unit 12a, the recording control unit 12b, the mode reception unit 12c, the position reception unit 12d, and the position change unit 12e. The processor is not limited to a single CPU; it may be configured to perform processing using multiple CPUs or hardware circuits such as ASICs, or it may be configured so that the CPU and hardware circuits cooperate in performing processing.

[0011] The display unit 13 is a means for displaying visual information and is composed of, for example, a liquid crystal display or an organic EL display. The display unit 13 may also include a display and a drive circuit for driving the display. The operation reception unit 14 is a means for receiving input from the user and is implemented by, for example, physical buttons, a touch panel, a mouse, or a keyboard. Of course, the touch panel may be implemented as a function of the display unit 13. The display unit 13 and the operation reception unit 14 together may be called the operation panel of the recording system 10.

[0012] The storage unit 15 is, for example, a hard disk drive, a solid-state drive, or other memory-based storage means. The storage unit 15 may be considered as a part of the memory possessed by the control unit 11. Alternatively, the storage unit 15 may be considered as a part of the control unit 11. The communication IF 16 is a general term for one or more IFs that allow the recording system 10 to communicate with external devices via wired or wireless connection in accordance with a predetermined communication protocol that includes a known communication standard. External devices include, for example, communication devices such as personal computers, servers, smartphones, and tablet terminals.

[0013] The transport unit 17 is a means for transporting the medium 30 along a predetermined transport direction under the control of the control unit 11. The transport unit 17 includes, for example, rollers that rotate to transport the medium 30, and a motor as a power source for rotation. Alternatively, the transport unit 17 may be a mechanism that transports the medium 30 by mounting it on a belt or pallet moved by a motor. The medium 30 is, for example, paper, but can be any medium that can be used for liquid recording, and may be made of materials other than paper, such as film or fabric.

[0014] The carriage 18 is a moving means that, under the control of the control unit 11, moves back and forth along a predetermined main scanning direction using the power of a carriage motor (not shown). The main scanning direction and the transport direction intersect. The carriage 18 is also equipped with a recording head 19. The recording head 19 is a means of recording by ejecting liquid onto the medium 30 using an inkjet method under the control of the control unit 11. The liquid is mainly ink, but the recording head 19 can also eject liquids other than ink. The movement of the carriage 18 and the movement of the recording head 19 are synonymous. The carriage 18 and the recording head 19 may be considered together as the recording head 19 without distinction.

[0015] The recording system 10 is realized by connecting a plurality of devices and apparatuses so that they can communicate with each other. The recording system 10 includes, for example, an information processing apparatus that plays the role of the control unit 11, and a printer that includes a conveyance unit 17, a carriage 18, and a recording head 19 and executes recording under the control of the information processing apparatus. In this case, the information processing apparatus can be understood as a recording control apparatus, an image processing apparatus, or the like. The storage unit 15 may be a part of the information processing apparatus or the printer, or may be neither a part of the information processing apparatus nor the printer, but a storage device accessible from the information processing apparatus and the printer. Similarly, the display unit 13 and the operation reception unit 14 may be a part of the information processing apparatus or the printer, or may be peripheral devices connected to the information processing apparatus or the printer. Alternatively, the recording system 10 may be configured to be realized by a single printer including the control unit 11. When the recording system 10 is realized by a single apparatus, it can be called the recording apparatus 10.

[0016] FIG. 2 simply shows the relationship between the medium 30 and the recording head 19 etc. from a top view. As described above, the recording head 19 is mounted on the carriage 18, and together with the carriage 18, it can perform a forward movement which is a movement from one side to the other side along the main scanning direction D1, and a return movement which is a movement from the other side to the one side. The recording head 19 has a plurality of nozzles 20 for discharging a liquid such as ink. Each of the white circles shown in FIG. 2 is an individual nozzle 20. The droplets discharged from the nozzle 20 are called dots.

[0017] The recording head 19 has nozzle groups for each type of liquid. The recording head 19 can discharge a plurality of colors of ink such as cyan (C), magenta (M), yellow (Y), and black (K), for example. In addition to CMYK inks, the recording head 19 may also discharge various liquids such as various inks such as light cyan (Lc), light magenta (Lm), etc., and a coating liquid, a reaction liquid, etc. The recording head 19 may be called a liquid discharge head, a printing head, a printing head, an inkjet head, etc.

[0018] In FIG. 2, four nozzle groups 21C, 21M, 21Y, and 21K are described very simply. A nozzle group corresponding to one type of liquid is composed of a plurality of nozzles 20 with a constant or substantially constant nozzle pitch, which is the interval between the nozzles 20 in the conveyance direction D2. The main scanning direction D1 and the conveyance direction D2 are orthogonal or substantially orthogonal. The nozzle group 21C is a nozzle row composed of a plurality of nozzles 20 that discharge C ink. Similarly, the nozzle group 21M is a nozzle row composed of a plurality of nozzles 20 that discharge M ink, the nozzle group 21Y is a nozzle row composed of a plurality of nozzles 20 that discharge Y ink, and the nozzle group 21K is a nozzle row composed of a plurality of nozzles 20 that discharge K ink.

[0019] In FIG. 2, the nozzle arrangement direction in which a plurality of nozzles 20 constituting the same nozzle group are arranged is parallel to the conveyance direction D2. However, depending on the configuration of the recording head 19, the nozzle arrangement direction may intersect obliquely with respect to the conveyance direction D2. The conveyance unit 17 conveys the medium 30 from the upstream to the downstream in the conveyance direction D2. The upstream and downstream in the conveyance direction D2 are simply referred to as upstream and downstream. A plurality of nozzle groups such as the nozzle groups 21C, 21M, 21Y, and 21K included in the recording head 19 are arranged along the main scanning direction D1 and have the same position in the conveyance direction D2. [[ID=,8]]

[0020] The control unit 11 causes the recording head 19 to discharge ink onto the medium 30 based on the recording data representing the image. As is known, in the recording head 19, a driving element is provided for each nozzle 20, and by controlling the application of a driving signal to the driving element of each nozzle 20 according to the recording data, each nozzle 20 discharges dots or does not discharge dots, and the image represented by the recording data is recorded on the medium 30. When referring to the configuration of FIG. 2, the recording data is data that defines dot discharge or non-dot discharge for each pixel and for each of the CMYK inks. Dot discharge is also referred to as dot on, and dot non-discharge is also referred to as dot off.

[0021] The liquid ejection by the recording head 19 accompanying the movement of the carriage 18 is called a path or main scan. The path caused by the forward movement of the carriage 18 is called the forward path, and the path caused by the return movement of the carriage 18 is called the return path. Recording performed in both the forward and return paths is called bidirectional recording, while recording performed in only one of the forward or return paths is called unidirectional recording.

[0022] The control unit 11 records the image represented by the recording data onto the medium 30 by combining the path of the carriage 18 and recording head 19 with the transport unit 17's transport of the medium 30 over a predetermined distance, which is known as paper feeding. The transport of the medium 30 by the transport unit 17 corresponds to the relative movement of the recording head 19 and the medium 30 in the transport direction D2, and this is also called sub-scanning.

[0023] The control unit 11 can also vary the size of the dots ejected by the nozzle 20 by changing the amplitude and shape of the drive signal applied to the drive element of the nozzle 20 according to the recorded data. The size of the dot can be the diameter of the dot or the volume per dot. For example, the nozzle 20 can eject three types of dots called large dots, medium dots, and small dots. The relationship between the sizes is small dot < medium dot < large dot. The nozzle 20 can eject two types of dots, or four or more types. Therefore, the dot-on data in the recorded data may be data indicating that the dot-on is of any size.

[0024] 2. Recording control processing: Figure 3 shows a flowchart illustrating the recording control process executed by the control unit 11 according to the program 12. In step S100, the control unit 11 acquires recording conditions for recording an image onto the medium 30. In this embodiment, the recording conditions are a concept that includes a recording mode. The control unit 11 has multiple recording modes and can perform recording according to a recording mode specified externally. Examples of recording modes include a "high-quality mode" that achieves relatively high image quality, a "normal mode" that reduces the recording time by lowering the image quality compared to the high-quality mode, and a "quick mode" that further reduces the image quality and shortens the recording time compared to the normal mode. Of course, the names and types of recording modes are not limited. The image quality and recording time for each recording mode differ depending on differences in various elements, such as the number of passes performed per a certain area of ​​the medium 30, the recording resolution, the movement speed of the carriage 18, and the transport speed of the medium 30 by the transport unit 17. Users can intuitively select a recording mode from the names of these recording modes without having to specify the recording conditions in detail.

[0025] Other recording conditions include, for example, double-sided or single-sided recording of the medium 30, color or monochrome recording, bordered or borderless recording, medium type, medium size, and so on. The control unit 11 can also identify a single recording mode from a specified combination of these recording conditions according to predetermined rules. The control unit 11 acquires the recording conditions, for example, through the operation reception unit 14 or the display unit 13. In other words, the user can arbitrarily specify recording conditions, including the recording mode, by operating on a UI screen (not shown) displayed on the display unit 13, and the control unit 11 acquires the specified recording conditions. UI stands for User Interface.

[0026] In step S110, the control unit 11 acquires image data representing the image to be recorded. The control unit 11 acquires image data instructed by the user through operation of the operation reception unit 14 from an image data storage location such as the storage unit 15 or memory inside or outside the recording system 10. Alternatively, the control unit 11 receives and acquires image data transmitted from an external device via the communication IF 16.

[0027] The execution order of steps S100 and S110 does not have to be as shown in Figure 3; step S110 may precede step S100, or they may be performed simultaneously or almost simultaneously. For example, if a recording execution instruction sent from an external device to the recording system 10 includes information specifying recording conditions and image data, steps S100 and S110 may be completed when the control unit 11 acquires such a recording execution instruction.

[0028] In step S120, the recording data generation unit 12a of the control unit 11 performs a color conversion process on the image data acquired in step S110. The image data acquired in step S110 corresponds to the "input data". The recording data generation unit 12a may perform a resolution conversion process or the like on the image data as needed. Through the color conversion process, the recording data generation unit 12a converts the color of each pixel constituting the image data into a grayscale value that represents the discharge amount of each liquid used by the recording head 19. This discharge amount may also be called the recording amount, recording rate, duty cycle, injection amount, etc.

[0029] The color space used by the image data is not particularly limited, but for example, let's assume that the color of each pixel in the image data is represented by gradation values ​​in the RGB color space of red (R), green (G), and blue (B). Also, as shown in the example in Figure 2, the recording head 19 can record using CMYK ink. In this case, the recording data generation unit 12a refers to the color conversion LUT 40, which defines the conversion relationship between RGB and CMYK, and converts the RGB gradation values ​​of each pixel in the image data to CMYK gradation values. LUT stands for lookup table. In the following explanation, we will continue assuming that the gradation values ​​are represented by 256 gradations from 0 to 255. The color conversion LUT 40 is stored in the storage unit 15 in advance. For the color of a pixel in the image data, the sum of the CMYK ink gradation values ​​obtained by the color conversion process, i.e., C + M + Y + K, is the "total ejection amount" corresponding to that color. Therefore, the control unit 11 determines the total amount of liquid discharged corresponding to the color of the input data, and controls the discharge of liquid by the recording head 19 based on the determined total amount of liquid discharged. In other words, it can be said that the control unit 11 controls the discharge of liquid by the recording head 19 based on the total amount of liquid discharged corresponding to the color of the input data.

[0030] In inkjet recording using nozzle 20, such ejection amounts cannot be used directly for recording. Therefore, in step S130, the recording data generation unit 12a performs halftone processing on the image data after color conversion processing to generate recording data that defines dot-on or dot-off for each pixel and each CMYK ink. Halftone processing can be performed using methods such as dithering or error diffusion. Of course, instead of binarization that only determines dot-on or dot-off for each pixel and each CMYK ink, multi-level processing may be performed, such as determining dot-on as large dot, medium dot, or small dot.

[0031] In step S140, the recording control unit 12b of the control unit 11 starts controlling the carriage 18, the recording head 19, and the transport unit 17, and transfers the recording data generated via step S130 to the recording head 19, causing the recording head 19 to eject dots corresponding to the recording data, thereby recording onto the medium 30. Of course, this recording is performed according to the recording conditions, including the recording mode, acquired in step S100. This concludes the flowchart in Figure 3.

[0032] 3. Features of the color conversion LUT: The characteristics of the color conversion LUT 40 used in the color conversion process of step S120 will be explained. Figure 4 shows a simplified representation of a portion of the color conversion LUT 40 in the RGB color space. According to Figure 4, the R, G, and B axes, each with a grayscale range of 0 to 255, are orthogonal to each other. The color conversion LUT 40 stores CMYK grayscale values ​​as output amounts, corresponding to multiple adjacent grid points spaced apart in the RGB color space. The CMYK grayscale values ​​are not shown in Figure 4.

[0033] The recording data generation unit 12a outputs the CMYK gradation value stored at a grid point as the color conversion result for a pixel if the RGB values ​​of a pixel in the image data match any of the grid points where the color conversion LUT 40 stores CMYK gradation values. On the other hand, if the RGB values ​​of a pixel in the image data do not match any of the grid points where the color conversion LUT 40 stores CMYK gradation values, the unit outputs the color conversion result for that pixel by performing an interpolation operation that references the CMYK gradation values ​​stored at multiple grid points in the vicinity of the RGB values ​​of that pixel. The interpolation operation can employ known interpolation methods such as bilinear interpolation and bicubic interpolation.

[0034] It is not practical for a color conversion LUT to have output values ​​for all combinations of RGB, each with a grayscale range of 0 to 255, considering the processing load required for LUT generation and the memory capacity required for LUT storage. Generally, such LUTs have output values ​​for each grid point, which is a combination of three axes of 17 grayscale values ​​obtained by dividing each RGB axis, for example, into 16 equal parts.

[0035] In contrast to such conventional configurations, the color conversion LUT 40 of this embodiment ensures that "adjacent grid points," which are grid points adjacent to the grid point of the darkest part of the color space, are located in a predetermined "first range" close to the darkest part. The first range is the range of 1 / 25.5 or less excluding the darkest part, where the darkest part is 0 and the brightest part of the color space is 1. Since the gradation range is 0 to 255, the first range is the range of gradation values ​​of 10 or less excluding the darkest part. If the gradation range is expressed in 512 gradations, the first range is the range of gradation values ​​of 20 or less excluding the darkest part.

[0036] According to Figure 4, the grid point (R,G,B)=(0,0,0) indicated by the black circle is the darkest part. The color of the darkest part can be understood as black. The dashed line indicates a part of the gray axis connecting the darkest and brightest parts of the RGB color space. The brightest part is (R,G,B)=(255,255,255), and the color can be understood as white. For clarity, adjacent grid points in color conversion LUT40 are indicated by white circles in Figure 4. In the example in Figure 4, adjacent grid points have RGB gradation values ​​of 0 or 5. That is, the seven grid points (R,G,B)=(5,0,0),(0,5,0),(0,0,5),(5,5,0),(5,0,5),(0,5,5),(5,5,5) are adjacent grid points. All of these adjacent grid points are within the first range. In Figure 4, other grid points that are further from the darkest area than adjacent grid points are omitted from the description.

[0037] Figure 5A shows color conversion LUT 50 as a comparative example to color conversion LUT 40 of this embodiment, and Figure 5B shows color conversion LUT 51 as a comparative example. Figure 6A shows color conversion LUT 52 as a comparative example. On the other hand, Figure 6B shows an example of the color conversion LUT 40 of this embodiment.

[0038] Since the interpretation of Figures 5A, 5B, 6A, and 6B is the same, we will first explain the basic interpretation of Figures 5A, 5B, 6A, and 6B (hereinafter referred to as Figure 5A, etc.). In Figure 5A, etc., the horizontal axis shows the grayscale values ​​of the image data as input data, and the vertical axis shows the output amount. In addition, Figure 5A, etc. shows the correspondence between input and output on the grayscale axis of the color conversion LUT. As mentioned above, the output amount is the grayscale value of CMYK, but in Figure 5A, etc., the output amount is displayed as a percentage. In other words, the grayscale range of 0 to 255 corresponds to 0% to 100%.

[0039] Furthermore, in Figure 5A, etc., the black circles correspond to grid points on the gray axis. Each black circle at the same position along the horizontal axis indicates the discharge amount corresponding to the same single grid point. Specifically, black circles connected by dashed lines indicate the discharge amount of K ink, black circles connected by dashed lines indicate the sum of the discharge amounts of CMY inks other than K, and black circles connected by solid lines indicate the sum of the discharge amounts of CMYK inks, i.e., the total discharge amount. According to Figure 5A, etc., for grid points with a horizontal gradation value of 0, i.e., the darkest areas, the discharge amount of K ink is set to 100%, and the discharge amount of CMY ink is set to 0%.

[0040] The color conversion LUT 50 shown in Figure 5A is a very common color conversion LUT, with uniform or nearly uniform spacing between grid points across the input grayscale range of 0 to 255. The color conversion LUT 51 shown in Figure 5B has an increased number of grid points in the relatively dark range of the input gradation compared to color conversion LUT 50. Therefore, the interpolation accuracy of the ejection amount for colors in such dark ranges is improved. However, increasing the number of grid points leads to problems such as an increased processing load required for LUT generation and increased consumption of memory capacity for LUT storage. In addition, with color conversion LUTs 50 and 51, the total ejection amount is only slightly over 100% in some gradation ranges of the input, so insufficient ink is likely to be impregnated into the medium 30, i.e., the medium surface is not sufficiently filled, in the dark parts of the image.

[0041] The color conversion LUT 52 shown in Figure 6A has the same number of grid points as the color conversion LUT 50, and the spacing between grid points is also uniform or nearly uniform, similar to the color conversion LUT 50. In the color conversion LUT 52, the total amount of ink ejected at grid point g1, which is closest to the grid point in the darkest area, is increased, mainly by increasing the ejection amount of CMY inks other than K ink. As a result, the insufficient ink output in the dark areas of the image is eliminated compared to the color conversion LUTs 50 and 51.

[0042] However, in color conversion LUT 52, the distance between the grid point in the darkest area and grid point g1 is the same as the distance between other grid points. Therefore, the interpolation accuracy of the output amount for colors near the darkest area is not high, and the media surface is still not sufficiently filled with colors near the darkest area. In photographic images, for example, shadows, hair of people, and other dark areas are often blackish colors that are slightly brighter than the darkest area, belonging to the first range described above. Therefore, the interpolation accuracy and media surface filling for colors belonging to the first range are particularly important for image quality. Colors belonging to the first range can be understood as colors near the darkest area. In Figures 6A and 6B, the first range is indicated by the symbol A. As shown in Figure 6A, in color conversion LUT 52, the position of grid point g1 is outside the first range A, so the problems of interpolation accuracy and media surface filling for colors near the darkest area are not resolved.

[0043] The color conversion LUT 40 solves each of the problems described with respect to such color conversion LUTs 50, 51, and 52. According to the color conversion LUT 40, the lattice point g1, which is an adjacent lattice point of the darkest part, is within the first range A. The lattice point g1 of the color conversion LUT 40 is one of the adjacent lattice points described in FIG. 4, and as a specific example, it may be understood that it corresponds to an adjacent lattice point of (R, G, B) = (5, 5, 5). And the total discharge amount of the lattice point g1 is the total discharge amount of the peak defined by the color conversion LUT 40, as is clear from FIG. 6B, and is more than the total discharge amount corresponding to the darkest part. According to FIG. 6B, the total discharge amount of the lattice point g1 is an amount exceeding 200%. Therefore, the control unit 11 controls the discharge of the liquid by the recording head 19 based on the total discharge amount of the liquid corresponding to the color of the input data (steps S120 to S140). In step S120, when a predetermined color belonging to the first range A in the color space of the input data is input as the color of the input data, the total discharge amount of the peak is determined. That is, when a predetermined color belonging to the first range A is input as the color of the input data, in steps S130 and S140, control is performed to discharge the total discharge amount of the peak by the recording head 19. The color of the lattice point g1 in the RGB color space shown in FIGS. 4 and 6B corresponds to a specific example of the predetermined color.

[0044] Also, the feature that the lattice point g1 is within the first range A can be grasped from the aspect that, as shown in FIG. 6B, when the distance between the lattice point of the darkest part and the lattice point g1, which is an adjacent lattice point, is D1 and the distance between lattice points other than the distance D1 is D2, D1 < D2 holds. That is, the number of lattice points does not change between the color conversion LUT 40 and the color conversion LUT 52. According to such a color conversion LUT 40, it is possible to accurately interpolate the discharge amount corresponding to the color in the vicinity of the darkest part without increasing the lattice points, and to determine the total discharge amount of the color in the vicinity of the darkest part to be a sufficient amount so as not to cause a filling shortage in the recording result.

[0045] Also, according to the color conversion LUT 40, since the total discharge amount in the darkest part where R = G = B = 0 is only K = 100%, that is, K = 255, there is no colored component mixed in black characters or ruled lines, and the quality of the blackness of the characters and ruled lines can be maintained. Note that FIG. 6B shows the discharge amounts corresponding to each lattice point located on the gray axis of the RGB color space. In the color conversion LUT 40, for example, it can be understood that the CMYK gradation values are such that the total discharge amount of adjacent lattice points on each of the R axis, G axis, and B axis is also the largest compared to other lattice points on the axis.

[0046] 4. Summary: As described above, according to this embodiment, the recording system 10 includes a recording head 19 having a plurality of nozzles 20 capable of discharging liquid onto the medium 30, and a control unit 11 that controls the recording head 19. The control unit 11 controls the discharge of the liquid by the recording head 19 based on the total discharge amount of the liquid corresponding to the color of the input data. When a predetermined color belonging to a first range in the color space of the input data is input as the color of the input data, the control unit 11 performs control to discharge the peak total discharge amount, and the peak total discharge amount is larger than the total discharge amount corresponding to the darkest part of the color space. The first range is a range of 1 / 25.5 or less excluding the darkest part when the darkest part is set to 0 and the brightest part of the color space is set to 1. <着

[0047] According to the above configuration, by setting the peak of the total discharge amount corresponding to a predetermined color belonging to the first range, the control unit 11 can eliminate the shortage of filling on the medium surface in the recording result for the color of the first range, which is a color near the darkest part, and can provide a recording result with good image quality.

[0048] Also, according to this embodiment, the recording system 10 has a LUT that stores the total discharge amount corresponding to each of a plurality of lattice points adjacent to each other at intervals in the color space. Then, the control unit 11 performs control to discharge the total discharge amount corresponding to the color of the input data by referring to the LUT. The LUT has an adjacent lattice point, which is a lattice point adjacent to the lattice point of the darkest part, in the first range. When the interval between the lattice point of the darkest part and the adjacent lattice point is D1, and the interval between lattice points other than the interval D1 is D2, D1 < D2 holds. According to the above configuration, in the situation of using a LUT having information on the total discharge amount associated with limited grid points in order to suppress the consumption of the memory capacity, the adjacent grid points are within the first range, and by setting D1 < D2, it is possible to solve the above-mentioned filling deficiency regarding the color in the vicinity of the darkest part without causing an increase in the data amount of the LUT.

[0049] The total discharge amount of the peak exceeds 200% in the example of FIG. 6B. Additional explanation will be given for such a total discharge amount of the peak. As an example, the total discharge amount of the peak is not less than the amount at which the medium 30 is not visually recognized in the recording result of an image of a predetermined area with the predetermined color onto the medium 30. Not visually recognizing the medium 30 means that the color of the medium 30 itself, for example, the white of the paper surface, cannot be seen. The predetermined color is the color represented by the RGB of the grid point g1 in FIG. 6B. Also, the image of a predetermined area is, for example, a color patch, specifically a color patch of 6 mm × 6 mm in length and width.

[0050] That is, it is assumed that the control unit 11 records image data representing a color patch, which is a set of pixels having the RGB of the grid point g1 in FIG. 6B, onto the medium 30 through color conversion processing referring to the color conversion LUT 40. At this time, when the recorded color patch is visually evaluated, within the range of the color patch, the surface of the medium is sufficiently covered with ink so that the color of the medium 30 cannot be visually recognized. According to the present embodiment, by setting the total discharge amount of the peak in this way, when recording the color in the vicinity of the darkest part, a recording result in which the medium 30 is sufficiently covered so that it cannot be visually recognized can be obtained.

[0051] The present embodiment discloses inventions in various categories, not limited to systems and apparatuses, including methods including each process executed by the system and apparatus, and programs 12 for causing a processor to execute the method.

[0052] 5. Modification example: The modification example included in the present embodiment will be described. According to the modification example, the recording system 10 has a position changing unit 12e, a mode receiving unit 12c, and a position receiving unit 12d as shown in FIG. 1. As described above, the color conversion LUT 40 may be stored in the storage unit 15 in advance, but the control unit 11 may generate the color conversion LUT 40 as needed. In other words, in the recording system 10, the position change unit 12e may be able to change the position of the grid points in the color space of the input data. For example, suppose the storage unit 15 has the color conversion LUT 52 shown in Figure 6A stored in advance. The position change unit 12e generates the color conversion LUT 40 from the color conversion LUT 52 by moving the adjacent grid points, including grid point g1, in the color conversion LUT 52 into a first range.

[0053] For example, in the color conversion LUT 52, when the grid point g1 is (R,G,B)=(16,16,16), the position change unit 12e changes the grid point g1 to one of the predetermined positions on the gray axis from (R,G,B)=(5,5,5) to (10,10,10) to create the color conversion LUT 40. On the gray axis, for example, (R,G,B)=(1,1,1) to (10,10,10) is the first range.

[0054] When the position of a grid point is changed, the position change unit 12e also changes the CMYK gradation values ​​stored in the color conversion LUT in association with the grid point. For grid point g1, the sum of the CMYK gradation values ​​is determined to some extent as the total output amount of the peak, for example, 200% or more. However, the position change unit 12e changes the ratio and sum of the CMYK gradation values ​​within such constraints to change the CMYK gradation values ​​to match the RGB color of the grid point g1 after the position change. For example, in the L*a*b* color space, which is an equipment-independent color space, the CMYK gradation values ​​that realize a color that approximates the color corresponding to the RGB of the grid point g1 after the position change within a predetermined color difference are stored in association with the grid point g1 after the position change. With this configuration, the control unit 11 can generate the color conversion LUT 40 according to this embodiment based on a certain color conversion LUT.

[0055] Figure 7 shows an example of a grid point position change process executed by the control unit 11 according to program 12, using a flowchart. The control unit 11 can execute the flowchart in Figure 7 in parallel with a part of the flowchart in Figure 3, or at a different timing than the flowchart in Figure 3.

[0056] In step 200, the position change unit 12e determines whether or not it is necessary to change the position of an adjacent grid point. If it is necessary to change the position of an adjacent grid point, the determination is "Yes" and the process proceeds to step S210. On the other hand, if it is not necessary to change the position of an adjacent grid point, the determination is "No" and the flowchart in Figure 7 ends. However, the position change unit 12e may repeat the determination in step S200 as needed until it determines "Yes" in step S200.

[0057] The specific methods for making a determination using step S200 are mainly the following three: The position receiving unit 12d can accept the specification of the position of an adjacent grid point. In other words, the user can arbitrarily specify the position of an adjacent grid point by operating the operation receiving unit 14, and the position receiving unit 12d accepts this specification. Through the UI screen, the user can specify the position of an adjacent grid point from the default position to, for example, any of the grayscale values ​​from 5 to 10. The default position is a position outside the first range, and the grayscale values ​​from 5 to 10 are positions within the first range.

[0058] Therefore, when the position receiving unit 12d receives a position specification within the first range, the position changing unit 12e determines "Yes" in step S200 and proceeds to step S210. Then, in step S210, the position change unit 12e changes the position of the adjacent grid point according to the position specified by the position receiving unit 12d. For example, if the position of the adjacent grid point is specified as having a grayscale value of 5, the position of the adjacent grid point is changed to a position corresponding to a grayscale value of 5 in the RGB color space as shown in Figure 4. The change of the position of the adjacent grid point to within the first range and the generation of the color conversion LUT 40 as a result of this change have already been explained.

[0059] In step S220, the position change unit 12e saves the color conversion LUT 40 generated by the position change in step S210 to the storage unit 15, thus completing the flowchart in Figure 7. Thereafter, the recording data generation unit 12a can use the color conversion LUT 40 to perform the color conversion process in step S120 of Figure 3. With this configuration, the positions of adjacent grid points can be adjusted according to the user's preference. As a result, the image quality of the colors near the darkest areas also becomes the image quality desired by the user.

[0060] Instead of changing the position of adjacent grid points according to the user's wishes, the position change unit 12e may change the position of adjacent grid points according to the darkest color in the input data, excluding the darkest area. Specifically, triggered by the acquisition of image data in step S110 of Figure 3, the position change unit 12e identifies the darkest color in the image data, excluding the darkest area where R=G=B=0 (hereinafter referred to as the quasi-darkest area). If the quasi-darkest area is a color that falls within the first range, the position change unit 12e determines "Yes" in step S200 and proceeds to step S210. On the other hand, if the quasi-darkest area is not a color that falls within the first range, the color conversion LUT 52 can be used as is, and therefore the position change unit determines "No" in step S200.

[0061] In step S210, the position changing unit 12e changes the position of adjacent grid points according to the quasi-darkest area. For example, if the quasi-darkest area is a color with a gradation value of 8, the position of grid point g1 is changed to a position corresponding to a gradation value of 8 on the gray axis in the RGB color space. The positions of adjacent grid points other than grid point g1 are also changed to positions within the first range corresponding to a gradation value of 8. The change of adjacent grid point positions to the first range and the generation of the color conversion LUT 40 as a result of this change have already been explained. With this configuration, the position of adjacent grid points can be adjusted according to the near-darkest areas of the input data. As a result, the image quality of the colors near the darkest areas is optimized according to the input data.

[0062] Alternatively, the position change unit 12e may change the position of adjacent grid points according to the specified recording mode. The mode reception unit 12c can accept the specification of a recording mode. As described above, since the user can arbitrarily specify a recording mode through the UI screen, the mode reception unit 12c accepts such a recording mode specification. If the recording mode accepted by the mode reception unit 12c is a predetermined mode for achieving relatively high image quality, such as the "clean mode" described above, the position change unit 12e determines "Yes" in step S200 and proceeds to step S210. On the other hand, if the recording mode accepted by the mode reception unit 12c is not one of the predetermined modes, the position change unit 12e determines "No" in step S200. The change of the position of adjacent grid points to within the first range and the generation of the color conversion LUT 40 as a result of this change are as already described. With this configuration, the positions of adjacent grid points can be adjusted according to the recording mode, so that the image quality that the recording mode aims to achieve is accurately realized in the recording result.

[0063] In such modified examples, it is also possible to combine multiple specific examples. For example, the position change unit 12e may determine "Yes" in step S200 and execute step S210 if the specified recording mode is a predetermined mode such as clean mode and the user has specified the position of an adjacent grid point. Alternatively, the unit may determine "Yes" in step S200 and execute step S210 if the specified recording mode is a predetermined mode such as clean mode, or if the user has specified the position of an adjacent grid point.

[0064] Furthermore, the position change unit 12e may determine "Yes" in step S200 and execute step S210 if the specified recording mode is a predetermined mode such as clean mode and the near-darkest part of the input data is a color that falls within the first range. Alternatively, the unit may determine "Yes" in step S200 and execute step S210 if the specified recording mode is a predetermined mode such as clean mode, or if the near-darkest part of the input data is a color that falls within the first range.

[0065] As described above, the position changing unit 12e not only generates a color conversion LUT by changing the position of adjacent grid points into the first range based on a color conversion LUT in which adjacent grid points are outside the first range, but it can also regenerate a color conversion LUT by changing the position of adjacent grid points to a different position within the first range, depending on the position specified by the user, the position of the quasi-darkest part of the image, or the type of recording mode, based on a color conversion LUT in which adjacent grid points are within the first range. Furthermore, the position changing unit 12e can also change the positions of grid points other than the grid points of the darkest part and adjacent grid points in conjunction with the change in the position of adjacent grid points. However, even in that case, the position change is performed so that the interval D1 < interval D2 is maintained.

[0066] The color space of the input data is not limited to the RGB color space; it may also be the CMYK color space. In other words, the color conversion process may be a process of converting from CMYK to CMYK output amounts, or a process of converting from CMYK to CMYKLcLm output amounts. Assume that the color space of the input data is the CMYK color space and that each color is represented by 256 gradations. In this case, the darkest part of the color space is the grid point C=M=Y=K=255, and the brightest part is the grid point C=M=Y=K=0. When the darkest part is set to 0 and the brightest part to 1, the range of 1 / 25.5 or less excluding the darkest part should be considered the first range.

[0067] The color conversion process may be performed using a function that defines a conversion rule from input to output, rather than using a LUT that defines the conversion relationship from input to output for multiple grid points. The carriage 18 may be capable of reciprocating not only along the main scanning direction D1, but also along the transport direction D2 which intersects the main scanning direction D1. In other words, the carriage 18 may move two-dimensionally within a plane parallel to the surface of the stationary medium 30 to perform recording on the medium 30. Alternatively, the recording system 10 may not have a carriage 18. That is, the recording head 19 may be stationary on the transport path of the transport unit 17, and the nozzle arrangement direction may be directed towards direction D1 rather than towards direction D2 as shown in Figure 2, and the recording may be performed by discharging liquid onto the medium 30 passing beneath the recording head 19. [Explanation of Symbols]

[0068] 10...Recording system, 11...Control unit, 12...Program, 12a...Recording data generation unit, 12b...Recording control unit, 12c...Mode reception unit, 12d...Position reception unit, 12e...Position change unit, 13...Display unit, 14...Operation reception unit, 15...Storage unit, 16...Communication IF, 17...Transport unit, 18...Carriage, 19...Recording head, 20...Nozzle, 21C, 21M, 21Y, 21K...Nozzle group, 30...Media, 40...Color conversion LUT, A...First range

Claims

1. A recording head having multiple nozzles capable of dispensing liquid onto a medium, A recording system including a control unit for controlling the recording head, The control unit, Based on the total amount of liquid discharged corresponding to the color of the input data, the recording head controls the discharge of the liquid. When a predetermined color belonging to a first range in the color space of the input data is input as the color of the input data, control is performed to discharge the peak total discharge amount. The peak total discharge volume is greater than the total discharge volume corresponding to the darkest part of the color space. The recording system is characterized in that the first range is a range of 1 / 25.5 or less excluding the darkest part, when the darkest part is defined as 0 and the brightest part of the color space is defined as 1.

2. The recording system according to claim 1, characterized in that the peak total discharge amount is greater than or equal to the amount that prevents the medium from being visible in the recording result of an image of a predetermined area of ​​a predetermined color on the medium.

3. The color space has a lookup table that stores the total discharge amount corresponding to each of a plurality of adjacent grid points spaced apart, The control unit controls the discharge of the total amount corresponding to the color of the input data by referring to the lookup table. The aforementioned lookup table is The first range includes adjacent grid points that are adjacent to the grid points in the darkest area, The recording system according to claim 1 or 2, characterized in that when the interval between the grid point in the darkest area and the adjacent grid point is D1, and the interval between grid points other than those with interval D1 is D2, then D1 < D2.

4. The recording system according to claim 3, further comprising a position changing unit capable of changing the position of the grid points in the color space.

5. The system includes a position receiving unit capable of receiving the specification of the position of the adjacent grid point, The recording system according to claim 4, characterized in that the position changing unit changes the position of the adjacent grid point according to the position specified by the position receiving unit.

6. The recording system according to claim 4, characterized in that the position changing unit changes the position of the adjacent grid points according to the darkest color among the colors included in the input data, excluding the darkest part.

7. It is equipped with a mode reception unit that can accept the specification of the recording mode, The recording system according to any one of claims 4 to 6, characterized in that the position changing unit changes the position of the adjacent grid points according to the recording mode specified by the mode receiving unit.

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