Printing apparatus, control method of printing apparatus, and storage medium

Abstract

To reduce the deviation of the use frequency of a nozzle when pseudo halftone processing is applied to an inkjet recorder.SOLUTION: The recording apparatus includes a selection unit configured to select a recording pattern corresponding to a gradation level for each pixel from a plurality of types of recording patterns prepared in advance by performing a pseudo halftone process on an input image, a setting unit configured to set a driving order of N nozzles capable of being driven in each of M nozzle arrays, a division unit configured to divide recording data including the driving order of the N nozzles into M groups each of which is obtained by dividing the recording data by shifting the driving order of the N nozzles by N / M, an assignment unit configured to assign or select the partial recording data obtained by dividing the recording data into the M groups to the M nozzle arrays, and a change unit configured to change the recording pattern to be assigned or selected according to the driving order of the nozzles in a case where recording is performed using the fixed recording pattern.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to bias in the frequency of nozzle use in a print head of a printing apparatus. [Background technology]

[0002] Inkjet printing devices have advantages such as easy compatibility with color inks, low noise during operation, high-quality printing, and compact size. As an example of a printing device, Patent Document 1 describes an inkjet printing device that can maintain printing quality while improving printing speed. In the inkjet printing device described in Patent Document 1, the nozzles of each nozzle array that ejects ink are divided into multiple groups, and printing data related to the nozzle drive order is divided for each nozzle group. The divided printing data is distributed and assigned to the multiple nozzle arrays. The nozzle drive order is then controlled so that ink dots ejected from the earliest nozzle in the drive order in each nozzle group of each nozzle array are aligned on the printing medium in a direction perpendicular to the scanning direction.

[0003] Another high-quality printing technique is to perform pseudo-halftoning on an input image, which determines the gradation level for each pixel in the input image and selects and uses a printing pattern corresponding to the gradation level for each pixel from multiple types of printing patterns prepared in advance, thereby enabling printing at a higher resolution than the input image. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-30594 Summary of the Invention [Problem to be solved by the invention]

[0005] When the above-described pseudo-halftoning process is applied to the inkjet recording apparatus described in Patent Document 1, the bias in the frequency of nozzle use can become large. [Means for solving the problem]

[0006] A recording device according to one aspect of the present disclosure is an inkjet recording device equipped with a recording head having M nozzle arrays (M is a natural number of 2 or more) capable of ejecting ink of the same color, and includes a selection means for performing pseudo-halftoning on an input image to determine the gradation level for each pixel in the input image and selecting a recording pattern corresponding to the gradation level for each pixel from a plurality of types of recording patterns prepared in advance, a setting means for setting the driving order of N nozzles (N is a multiple of M) that can be driven in each of the M nozzle arrays by shifting the driving cycle by N / M nozzles between the M nozzle arrays, and a setting means for setting a driving order of N nozzles (N is a multiple of M) that can be driven in each of the M nozzle arrays by shifting the driving cycle by N / M nozzles between the M nozzle arrays. and a dividing means for dividing print data, including a nozzle drive sequence for printing at a higher resolution than the drive resolution of each nozzle in each of the nozzle arrays, into M groups obtained by shifting the drive sequence of the N nozzles by N / M; an allocating means for distributing and allocating partial print data obtained by dividing into the M groups to the M nozzle arrays in accordance with the nozzle drive sequence in each of the nozzle arrays; and a changing means for, when printing is performed using a fixed print pattern, allocating the partial print data in accordance with the nozzle drive sequence in each of the nozzle arrays or changing the selected print pattern. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to reduce bias in the frequency of nozzle use when applying pseudo-halftoning to an inkjet recording device. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view schematically illustrating a recording apparatus. [Figure 2] FIG. 2 is a schematic diagram showing an arrangement of nozzles in an ink ejection unit. [Figure 3] FIG. 2 is a block diagram showing a control system of the recording apparatus. [Figure 4] FIG. 2 is a block diagram showing the functional configuration of the recording apparatus. [Figure 5] FIG. 10 is a diagram illustrating the nozzle driving sequence in a comparative example. [Figure 6] FIG. 10 is a schematic diagram showing an example of a recording pattern representing multiple gradation levels. [Figure 7] 10A and 10B are diagrams illustrating print patterns and nozzle driving sequences when printing is performed by switching print patterns. [Figure 8] 10A and 10B are diagrams illustrating nozzles used in each nozzle array when printing is performed by switching print patterns. [Figure 9] 10A and 10B are diagrams illustrating print patterns and nozzle drive sequences when printing is performed with a fixed print pattern. [Figure 10] FIG. 10 is a diagram illustrating nozzles used in each nozzle array when printing is performed with a fixed print pattern. [Figure 11] 10 is a flowchart illustrating a control method for the recording apparatus. [Figure 12] FIG. 10 is a schematic diagram showing an example of a process for selecting a recording pattern. [Figure 13] FIG. 10 is a schematic diagram showing another example of the process of selecting a recording pattern. [Figure 14] FIG. 10 is a schematic diagram showing a modified example of the process of selecting a recording pattern. [Figure 15] 10A and 10B are diagrams illustrating print patterns and nozzle drive sequences when the allocation of partial print data in each nozzle array is changed. [Figure 16] 10A and 10B are diagrams illustrating nozzles used in each nozzle array when the allocation of partial print data in each nozzle array is changed. [Figure 17] 10A and 10B are diagrams illustrating the print pattern and the nozzle driving sequence when the print pattern is changed. [Figure 18] FIG. 10 is a diagram illustrating nozzles used in each nozzle array when the printing pattern is changed. [Figure 19] 10A and 10B are diagrams illustrating print patterns and nozzle drive sequences when printing is performed with a fixed print pattern. [Figure 20] FIG. 10 is a diagram illustrating nozzles used in each nozzle array when printing is performed with a fixed print pattern. [Figure 21] 10A and 10B are diagrams illustrating print patterns and nozzle drive sequences when the allocation of partial print data in each nozzle array is changed. [Figure 22] 10A and 10B are diagrams illustrating nozzles used in each nozzle array when the allocation of partial print data in each nozzle array is changed. [Figure 23] 10A and 10B are diagrams illustrating the print pattern and the nozzle driving sequence when the print pattern is changed. [Figure 24] FIG. 10 is a diagram illustrating nozzles used in each nozzle array when the printing pattern is changed. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the present disclosure, and not all of the combinations of features described in the present embodiments are necessarily essential to the solutions of the present disclosure. In addition, the same components will be designated by the same reference numerals and descriptions thereof will be omitted.

[0010] <<First Embodiment>> <Configuration of recording device> Fig. 1 is a perspective view that schematically shows an inkjet recording apparatus 100 (hereinafter referred to as recording apparatus 100) according to this embodiment. As shown in Fig. 1, the recording apparatus 100 according to this embodiment includes a recording head 101, a transport roller 103, an auxiliary roller 104, a pair of feed rollers 105, and a carriage 106. The recording apparatus 100 records an image on the recording medium MD by ejecting ink from the recording head 101 and causing the ink to land on the recording medium MD.

[0011] The recording medium MD may be any material capable of recording an image by impacting ink droplets thereon. Examples of the recording medium MD include sheet materials such as recording paper, plastic sheets, and overhead projector sheets. In Figures 1 and 2, the Z direction indicates the vertical direction and intersects (orthogonal in this embodiment) with the XY plane defined by the X and Y directions.

[0012] The print head 101 is capable of ejecting four colors of ink: black (K), cyan (C), magenta (M), and yellow (Y). The print head 101 includes four ink tanks 120 and an ink ejection unit 130. Each ink tank 120 stores a corresponding color of ink among the four colors. The ink ejection unit 130 includes a plurality of nozzle arrays 301-310 (see FIG. 2) in which nozzles for ejecting ink are arranged. Each nozzle of the ink ejection unit 130 is provided with an electrothermal conversion element (ejection element), not shown. The electrothermal conversion element applies thermal energy to the ink using an electric pulse, causing the ink to be ejected from the nozzle.

[0013] FIG. 2 is a schematic diagram showing the arrangement of nozzles in the ink ejection unit 130. In the ink ejection unit 130, first to tenth nozzle rows 301 to 310 are arranged in order from the right side (+X direction side) of FIG. 2. Each nozzle row of the ink ejection unit 130 is capable of ejecting a corresponding color ink from among the four colors of ink supplied from the four ink tanks 120. For example, the first nozzle row 301 and the tenth nozzle row 310 eject the same color ink (e.g., cyan ink) from among the four colors of ink. The second nozzle row 302 and the ninth nozzle row 309 eject the same color ink (e.g., magenta ink) from among the four colors of ink. The third nozzle row 303 and the eighth nozzle row 308 eject the same color ink (e.g., yellow ink) from among the four colors of ink. The fourth nozzle row 304, the fifth nozzle row 305, the sixth nozzle row 306, and the seventh nozzle row 307 eject black ink out of the four color inks.

[0014] The first nozzle row 301 and the tenth nozzle row 310 are arranged symmetrically with respect to the center of the ink ejection section 130 (a plane extending in the YZ direction). The second nozzle row 302 and the ninth nozzle row 309 are arranged symmetrically with respect to the center of the ink ejection section 130. The third nozzle row 303 and the eighth nozzle row 308 are arranged symmetrically with respect to the center of the ink ejection section 130. The fourth nozzle row 304 and the seventh nozzle row 307 are arranged symmetrically with respect to the center of the ink ejection section 130. The fifth nozzle row 305 and the sixth nozzle row 306 are arranged symmetrically with respect to the center of the ink ejection section 130.

[0015] As shown in FIG. 1, the conveying roller 103 and the auxiliary roller 104 are formed to extend in the width direction (X direction) of the recording medium MD and sandwich the recording medium MD. The conveying roller 103 rotates in cooperation with the auxiliary roller 104 to convey the recording medium MD in the +Y direction. The pair of feed rollers 105 are formed to extend in the width direction (X direction) of the recording medium MD and sandwich the recording medium MD. The pair of feed rollers 105 rotate in opposite directions to each other, thereby moving the recording medium MD conveyed by the conveying roller 103 to a recording position below the recording head 101. The pair of feed rollers 105 also have the function of maintaining the recording medium MD in a flat state between the conveying roller 103 and the auxiliary roller 104. The conveying roller 103 and the pair of feed rollers 105 are driven by a conveying motor 243 (see FIG. 3).

[0016] As shown in FIG. 1, the carriage 106 supports the print head 101. The carriage 106 moves together with the print head 101 in a main scanning direction (X direction) that intersects (orthogonal in this embodiment) the arrangement direction of the nozzles in the print head 101. The carriage 106 is driven by a carriage motor 241 (see FIG. 3). When not performing a printing operation, the carriage 106 is located at a home position H indicated by a dashed line in FIG. 1. The carriage 106 is also located at the home position H when performing a recovery operation to maintain good ink ejection performance of the ink ejection unit 130.

[0017] When performing a printing operation, the carriage 106 moves in the +X direction from a home position H. As the carriage 106 passes over the printing medium MD, ink is ejected from multiple nozzles of the print head 101 (ink ejection unit 130), and an image is printed on a portion of the printing medium MD. When printing is performed only when the print head 101 moves in the +X direction, the carriage 106 performs a printing operation of moving from the end of the printing medium MD on the -X direction side to the end on the +X direction side, and then returns to the home position H and moves again in the +X direction. When printing is performed when the print head 101 moves in both the +X direction and the -X direction, the carriage 106 performs a printing operation of moving from the end of the printing medium MD on the -X direction side to the end on the +X direction side, and a printing operation of moving from the end on the +X direction side to the end on the -X direction. After one printing operation is completed and before the next printing operation is started, the conveying roller 103 and the pair of feed rollers 105 rotate, and the printing medium MD is conveyed a predetermined amount in the +Y direction. In this way, one printing operation and a predetermined amount of conveyance operation of the recording medium MD are repeated to print an image on one sheet of the recording medium MD. Note that one printing operation is also called one scan.

[0018] FIG. 3 is a block diagram showing the control system of the recording apparatus 100. As shown in FIG. 3, the recording apparatus 100 according to this embodiment further includes a controller 200, a switch group 220, a sensor group 230, a carriage motor driver 240, a transport motor driver 242, and a head driver 244. The controller 200 includes a CPU 201, a ROM 202, an ASIC 203, a RAM 204, a system bus 205, and an A / D converter 206. The CPU (Central Processing Unit) 201 controls the operation of each component of the recording apparatus 100 based on a program stored in the ROM 202. The ROM (Read Only Memory) 202 stores programs for implementing each process of this embodiment, predetermined tables, and other fixed data. The ASIC (Application Specific Integrated Circuit) 203 generates control signals for the carriage motor 241 and transport motor 243, and a control signal for the ink ejection unit 130. The RAM (Random Access Memory) 204 is provided with an area for developing image data to be recorded, a working area, etc. The system bus 205 interconnects the CPU 201, the ASIC 203, and the RAM 204 to transmit and receive data. The A / D converter 206 A / D converts analog signals input from the sensor group 230 and transmits the digital signals obtained by the A / D conversion to the CPU 201.

[0019] The controller 200 is electrically connected to a host device 210 provided outside the recording device 100 via an interface (I / F) 211. Examples of the host device 210 include a PC (Personal Computer), an image reader, and a digital camera. The recording device 100 receives image data, commands, status signals, and the like from the host device 210 via the interface 211 and transmits them to the controller 200. The switch group 220 is a group of switches for accepting operation inputs by an operator. The switch group 220 includes a power switch 221, a start switch 222 operated to instruct the start of a recording operation, and a recovery switch 223 operated to instruct a recovery operation. The sensor group 230 is a group of sensors for detecting the state of the recording device 100. The sensor group 230 includes a photocoupler 231 and a temperature sensor 232. The photocoupler 231 detects that the carriage 106 is located at the home position H. Temperature sensors 232 are provided at multiple locations on the recording apparatus 100 to detect temperature. A carriage motor driver 240 drives a carriage motor 241 based on a control signal sent from the controller 200. A transport motor driver 242 drives a transport motor 243 based on a control signal sent from the controller 200. A head driver 244 drives the nozzles (electrothermal conversion elements) of each nozzle row in the ink ejection unit 130 of the recording head 101 based on a control signal sent from the controller 200.

[0020] The controller 200 controls the ink ejection unit 130 of the print head 101 via the head driver 244 based on control signals generated by the ASIC 203. Print data for printing by the print head 101 is sent to the head driver 244 using the functions of the ASIC 203. The print data sent to the head driver 244 includes data related to the nozzle drive order when printing. In this embodiment, the print data including the nozzle drive order when printing is divided into multiple nozzle groups corresponding to the number of nozzle arrays that eject ink of the same color, and the data is distributed and assigned to the nozzle arrays that eject ink of the same color.

[0021] FIG. 4 is a block diagram showing the functional configuration of the controller 200 in the recording device 100. The controller 200 includes a selection unit 401, a setting unit 402, a division unit 403, an allocation unit 404, and a change unit 405. These functions are realized by the CPU 201 of the controller 200 executing a group of programs stored in the ROM 202. Therefore, while the CPU 201 can be said to have each of the functions of the controller 200 shown in FIG. 4, it is not necessary for the CPU 201 to have all of these functions. For example, the controller 200 may include a dedicated processing circuit that performs processing corresponding to at least one of the functions of the controller 200. In this embodiment, at least one of the functions of the controller 200 may exchange information with other functions by any method. For example, at least one of the functions of the controller 200 may store acquired or created information in the RAM 204, making the information available to other functions. In other words, in this embodiment, information exchange between the functions of the controller 200 may be performed via the RAM 204. Furthermore, at least one of the functions of the controller 200 may output acquired or created information to another function without storing it in the RAM 204.

[0022] The selection unit 401 performs pseudo-halftoning on an input image input from the host device 210 to the controller 200. Known methods for performing pseudo-halftoning include dithering and error diffusion. The selection unit 401 performs pseudo-halftoning on the input image to determine the gradation level for each pixel in the input image. The gradation levels determined by the pseudo-halftoning are multi-valued (e.g., five-valued) gradation levels. The selection unit 401 then selects a print pattern corresponding to the gradation level for each pixel from multiple print patterns prepared in advance. The print patterns corresponding to the gradation levels for each pixel will be described later. In this embodiment, the number of nozzle arrays ejecting ink of the same color is defined as M, and the number of drivable nozzles in each of the M nozzle arrays is defined as N. M is a natural number greater than or equal to 2, and N is a multiple of M. The number of drivable nozzles in each nozzle array is assumed to be the same as the number of nozzles arranged in the nozzle array. The setting means 402 sets the drive order of the N nozzles that can be driven in each nozzle row by shifting the drive cycle by N / M nozzles among the M nozzle rows.

[0023] The dividing means 403 divides the print data, including the nozzle drive order, for printing at a higher resolution than the drive resolution (described later) using the print pattern. The dividing means 403 divides the print data, including the nozzle drive order, into M groups of nozzles, obtained by shifting the drive order of N nozzles by N / M. The allocating means 404 distributes and allocates the partial print data obtained by dividing the print data into M groups of nozzles by the dividing means 403 to M nozzle arrays according to the nozzle drive order in each nozzle array. When printing is performed using a fixed print pattern, the changing means 405 changes the nozzles driven based on the partial print data distributed and allocated to the M nozzle arrays to other nozzles in the M nozzle arrays. In this embodiment, the changing means 405 changes the nozzles driven based on the partial print data to other nozzles in the M nozzle arrays in response to changing the allocation of the partial print data according to the nozzle drive order in each nozzle array set by the setting means 402.

[0024] <Comparative Example> Next, a comparative example of this embodiment will be described. FIG. 5 is a diagram illustrating the nozzle driving order in the comparative example. FIG. 5 shows ink dots formed when ink of the same color is ejected from the nozzles of the first nozzle array 301 and the nozzles of the tenth nozzle array 310. The numbers 1 to 16 arranged horizontally in FIG. 5 indicate the relative positions of ink dots formed on the recording medium MD in the main scanning direction (the direction intersecting the nozzle arrangement direction). The numbers 1 to 16 arranged vertically in FIG. 5 indicate the nozzle order counted from the end of the nozzle array. As mentioned above, the number of nozzle arrays ejecting ink of the same color is defined as M, and the number of nozzles that can be driven in each of the M nozzle arrays is defined as N. In the comparative example shown in FIG. 5, M=2 and N=16. In addition, ink dots that can be formed on the recording medium MD by driving the nozzles of the first nozzle array 301 are referred to as first ink dots A. Ink dots that can be formed on the recording medium MD by driving the nozzles of the tenth nozzle array 310 are referred to as second ink dots B. For example, the first ink dot A located in the first row and first column indicates an ink dot that can be formed by first driving the first nozzle counting from the end of the first nozzle array 301. The second ink dot B located in the first row and first column indicates an ink dot that can be formed by first driving the ninth nozzle counting from the end of the tenth nozzle array 310. The nozzle drive order is controlled so that the ink dots ejected from the earliest nozzle in the drive order in each nozzle group of each nozzle array are aligned on the recording medium MD in a direction perpendicular to the main scanning direction. When the same color ink is ejected from the nozzles of the first nozzle array 301 and the tenth nozzle array 310, the color and shape of the second ink dot B will be the same as the color and shape of the first ink dot A.

[0025] As shown in FIG. 5 , in the first nozzle array 301, a first ink dot A can be formed by driving the nozzles in the order of the first nozzle, the second nozzle, the third nozzle, the fourth nozzle, ..., and the sixteenth nozzle counting from the end. In the tenth nozzle array 310, a second ink dot B can be formed by driving the nozzles in the order of the ninth nozzle, the tenth nozzle, ..., and the sixteenth nozzle counting from the end, and then driving the nozzles in the order of the first nozzle, the second nozzle, ..., and the eighth nozzle. In this way, the nozzle driving order in the tenth nozzle array 310 is shifted by a half cycle compared to the first nozzle array 301. Here, the region in which ink dots are formed by the first through eighth driven nozzles in each nozzle array is referred to as a first region CM1. The region in which ink dots are formed by the ninth through sixteenth driven nozzles in each nozzle array is referred to as a second region CM2. In the first region CM1, first ink dots A may be formed by the first to eighth nozzles counting from the end of the first nozzle row 301, and second ink dots B may be formed by the ninth to sixteenth nozzles counting from the end of the tenth nozzle row 310. In the second region CM2, first ink dots A may be formed by the ninth to sixteenth nozzles counting from the end of the first nozzle row 301, and second ink dots B may be formed by the first to eighth nozzles counting from the end of the tenth nozzle row 310.

[0026] 5, the setting means 402 of the controller 200 sets the drive order of the 16 drivable nozzles in each nozzle array by shifting the drive cycle by eight nozzles (i.e., half a cycle) between two nozzle arrays that eject ink of the same color. Specifically, the setting means 402 sets the drive order of the nozzles in the first nozzle array 301 to the drive order of the 1st to 16th nozzles counting from the end of the first nozzle array 301. The setting means 402 sets the drive order of the nozzles in the tenth nozzle array 310 to the drive order of the 9th to 16th nozzles and the 1st to 8th nozzles counting from the end of the tenth nozzle array 310. The dividing means 403 of the controller 200 divides the print data including the nozzle drive order into two groups of nozzles, each group having a drive order shifted by eight nozzles. Specifically, the dividing means 403 divides the print data, including the nozzle drive order, into partial print data for the group of nozzles 1 through 8, counting from the end of the nozzle array, and partial print data for the group of nozzles 9 through 16. The allocation means 404 of the controller 200 distributes and allocates the partial print data obtained by dividing the print data into two nozzle groups by the dividing means 403 to two nozzle arrays according to the nozzle drive order in each nozzle array. For example, when forming ink dots in the first region CM1, the allocation means 404 allocates the partial print data for the group of nozzles 1 through 8, counting from the end of the nozzle array, to the first nozzle array 301. Meanwhile, the allocation means 404 allocates the partial print data for the group of nozzles 9 through 16, counting from the end of the nozzle array, to the tenth nozzle array 310. Also, for example, when forming ink dots in the second region CM2, the allocation means 404 allocates the partial print data for the group of nozzles 9 through 16, counting from the end of the nozzle array, to the first nozzle array 301. Meanwhile, the allocation means 404 allocates partial print data of the group of nozzles numbered 1 to 8, counting from the end of the nozzle row, to the tenth nozzle row 310. As a result, partial print data obtained by dividing the print data including the nozzle drive sequence is distributed and allocated to the two nozzle rows, and ink is ejected from the nozzles of each group based on the allocated partial print data.

[0027] Here, the density in the main scanning direction of the first ink dots A (or second ink dots B) formed per drive cycle is referred to as the drive resolution. The density of ink dots including the first ink dots A and the second ink dots B is referred to as the print resolution. According to the comparative example shown in FIG. 5, when the drive resolution is 300 dpi, the print resolution can be doubled to 600 dpi. Therefore, by setting the drive resolution to 300 dpi, which is half the print resolution, the movement speed of the carriage 106 in the main scanning direction can be increased, and the print speed can be increased. Furthermore, by setting the print resolution to 600 dpi, which is double the drive resolution, the print resolution can be increased, and print quality can be improved.

[0028] <Recording pattern> Next, we will explain the recording patterns corresponding to the gradation levels of each pixel obtained by the pseudo-halftoning process. FIG. 6 is a schematic diagram showing an example of a recording pattern representing multi-value (5-value) gradation levels. In this embodiment, level 0 is referred to as Lv0, level 1 as Lv1, level 2 as Lv2, level 3 as Lv3, and level 4 as Lv4. FIG. 6(a) is a schematic diagram showing an example of a recording pattern corresponding to pixel G0 having a gradation level of Lv0. FIG. 6(b) is a schematic diagram showing an example of a recording pattern corresponding to pixel G1 having a gradation level of Lv1. FIG. 6(c) is a schematic diagram showing an example of a recording pattern corresponding to pixel G2 having a gradation level of Lv2. FIG. 6(d) is a schematic diagram showing an example of a recording pattern corresponding to pixel G3 having a gradation level of Lv3. FIG. 6(e) is a schematic diagram showing an example of a recording pattern corresponding to pixel G4 having a gradation level of Lv4. For example, the gradation level of one pixel in a 300 dpi input image is represented by a 600 dpi recording pattern consisting of 2×2=4 pixels through pseudo-halftoning.

[0029] As shown in Figure 6(a), one type of Lv0 recording pattern K01 is obtained for pixel G0 having a gradation level of Lv0. Lv0 recording pattern K01 is a blank pattern (no dots arranged) consisting of four 2x2 pixels that represents the Lv0 gradation level.

[0030] As shown in FIG. 6(b), four types of Lv1 recording patterns are obtained for pixel G1 having a gradation level of Lv1. The Lv1 recording pattern is a dot pattern consisting of four 2x2 pixels representing the Lv1 gradation level. In the Lv1 recording pattern, a dot is placed in one of the four pixels. The Lv1 recording patterns include a first Lv1 recording pattern K11, a second Lv1 recording pattern K12, a third Lv1 recording pattern K13, and a fourth Lv1 recording pattern K14. In the first Lv1 recording pattern K11, a dot is placed in the upper left pixel in FIG. 6(b). In the second Lv1 recording pattern K12, a dot is placed in the lower right pixel in FIG. 6(b). In the third Lv1 recording pattern K13, a dot is placed in the upper right pixel in FIG. 6(b). In the fourth Level 1 recording pattern K14, a dot is placed in the bottom left pixel in FIG. 6(b).

[0031] As shown in FIG. 6(c), six types of Lv2 recording patterns are obtained for pixel G2 having a Lv2 gradation level. The Lv2 recording pattern is a dot pattern consisting of four 2x2 pixels representing the Lv2 gradation level. In the Lv2 recording pattern, dots are arranged in two of the four pixels. The Lv2 recording pattern includes a first Lv2 recording pattern K21, a second Lv2 recording pattern K22, and a third Lv2 recording pattern K23. Furthermore, the Lv2 recording pattern includes a fourth Lv2 recording pattern K24, a fifth Lv2 recording pattern K25, and a sixth Lv2 recording pattern K26. In the first Lv2 recording pattern K21, dots are arranged in the upper left pixel and the upper right pixel in FIG. 6(c). In the second Lv2 recording pattern K22, dots are arranged in the upper right pixel and the lower right pixel in FIG. 6(c). In the third Level 2 recording pattern K23, dots are placed in the bottom left and bottom right pixels in Figure 6(c). In the fourth Level 2 recording pattern K24, dots are placed in the top left and bottom left pixels in Figure 6(c). In the fifth Level 2 recording pattern K25, dots are placed in the top left and bottom right pixels in Figure 6(c). In the sixth Level 2 recording pattern K26, dots are placed in the top right and bottom left pixels in Figure 6(c).

[0032] As shown in FIG. 6(d), four types of Lv3 recording patterns are obtained for pixel G3 having a Lv3 gradation level. The Lv3 recording pattern is a dot pattern consisting of four 2x2 pixels representing the Lv3 gradation level. In the Lv3 recording pattern, dots are arranged in three of the four pixels. The Lv3 recording patterns include a first Lv3 recording pattern K31, a second Lv3 recording pattern K32, a third Lv3 recording pattern K33, and a fourth Lv3 recording pattern K34. In the first Lv3 recording pattern K31, dots are arranged in the upper left pixel, upper right pixel, and lower right pixel in FIG. 6(d). In the second Lv3 recording pattern K32, dots are arranged in the upper left pixel, upper right pixel, and lower left pixel in FIG. 6(d). In the third Level 3 recording pattern K33, dots are arranged in the upper left, lower left, and lower right pixels in Fig. 6(d). In the fourth Level 3 recording pattern K34, dots are arranged in the upper right, lower left, and lower right pixels in Fig. 6(d).

[0033] As shown in Figure 6(e), one type of Lv4 recording pattern K41 is obtained for pixel G4 having a gradation level of Lv4. The Lv4 recording pattern K41 is a dot pattern consisting of four 2x2 pixels that represent the Lv4 gradation level. In the Lv4 recording pattern K41, dots are placed in all four pixels.

[0034] <Recording using recording patterns> The recording device 100 according to this embodiment performs recording at a higher resolution than the driving resolution by applying a pseudo-halftone processing technique to the comparative example described above. This enables higher quality recording. The recording device 100 performs recording at a higher resolution than the input image by using a fixed recording pattern for a portion of the input image (e.g., an edge portion). The recording device 100 performs recording at a higher resolution than the input image by switching the recording pattern for each pixel of the input image for the remaining portion of the input image excluding the portion (e.g., an edge portion).

[0035] Fig. 7 is a diagram illustrating the print patterns and the nozzle drive order when printing is performed by switching print patterns. Fig. 8 is a diagram illustrating the nozzles used in each nozzle array when printing is performed by switching print patterns. In the examples shown in Figs. 7 and 8, M=2 and N=16. Furthermore, the resolution of the input image is 600 dpi, and the drive resolution is 600 dpi.

[0036] FIG. 7(a) is a schematic diagram showing a recording pattern for recording an input image at 600 dpi. FIG. 7(b) is a schematic diagram showing the arrangement of dots in the recording pattern when recording is performed by switching the recording pattern. The black circles in FIGS. 7(a) and 7(b) indicate the arrangement of dots in the recording pattern. When the gradation level of one pixel in the input image is Lv2, multiple recording patterns for recording are selected from pre-prepared Lv2 recording patterns, for example, from the six Lv2 recording patterns mentioned above. For example, as shown in FIG. 7(a), the fifth Lv2 recording pattern K25 and the sixth Lv2 recording pattern K26 are selected. Then, as shown in FIG. 7(b), the fifth Lv2 recording pattern K25 and the sixth Lv2 recording pattern K26 are alternately used to record the input image. The gradation level of one pixel in a 600 dpi input image is represented by a 1200 dpi recording pattern consisting of 2×2=4 pixels through pseudo-halftone processing.

[0037] FIG. 7(c) is a diagram illustrating the nozzle drive order when printing by switching print patterns. FIG. 7(c) illustrates ink dots formed when ink of the same color is ejected from the nozzles of the first nozzle array 301 and the nozzles of the tenth nozzle array 310. In the example shown in FIG. 7(c), the horizontal and vertical numbers 1 to 16 are the same as the horizontal and vertical numbers 1 to 16 in the comparative example shown in FIG. 5. The first ink dot A and the second ink dot B are the same as the first ink dot A and the second ink dot B in the comparative example shown in FIG. 5. The first region CM1 and the second region CM2 are the same as the first region CM1 and the second region CM2 in the comparative example shown in FIG. 5. As described above, the first ink dot A located in the first row and first column represents an ink dot that can be formed by first driving the first nozzle, counting from the end of the first nozzle array 301. The second ink dot B located in the first column of the ninth row indicates an ink dot that can be formed by first driving the ninth nozzle counting from the end of the tenth nozzle row 310. The nozzle driving order is controlled so that the ink dots ejected from the earliest nozzle in the driving order in the nozzle group of each nozzle row are aligned on the recording medium MD in a direction perpendicular to the main scanning direction.

[0038] As shown in FIG. 7( c), in the first nozzle array 301, a first ink dot A can be formed by driving the nozzles in the order of the first nozzle, the second nozzle, the third nozzle, the fourth nozzle, ..., and the sixteenth nozzle, counting from the end. In the tenth nozzle array 310, a second ink dot B can be formed by driving the nozzles in the order of the ninth nozzle, the tenth nozzle, ..., and the sixteenth nozzle, counting from the end, and then driving the nozzles in the order of the first nozzle, the second nozzle, ..., and the eighth nozzle. As in the comparative example shown in FIG. 5, in the tenth nozzle array 310, the nozzle driving order is shifted by a half period compared to the first nozzle array 301. In the first region CM1, a first ink dot A can be formed by the first through eighth nozzles, counting from the end, in the first nozzle array 301, and a second ink dot B can be formed by the ninth through sixteenth nozzles, counting from the end, in the tenth nozzle array 310. In the second region CM2, a first ink dot A can be formed by the 9th to 16th nozzles counting from the end of the first nozzle row 301, and a second ink dot B can be formed by the 1st to 8th nozzles counting from the end of the tenth nozzle row 310.

[0039] As in the comparative example shown in FIG. 5, the setting means 402 of the controller 200 sets the drive order of the 16 drivable nozzles in each nozzle array by shifting the drive cycle by eight nozzles (i.e., by half a cycle) between two nozzle arrays that eject ink of the same color. The division means 403 of the controller 200 divides the print data, including the nozzle drive order, into two groups of nozzles, each of which is obtained by shifting the drive order by eight nozzles. Specifically, the division means 403 divides the print data, including the nozzle drive order, into partial print data for the group of nozzles 1 through 8, counting from the end of the nozzle array, and partial print data for the group of nozzles 9 through 16. As in the comparative example shown in FIG. 5, the allocation means 404 of the controller 200 distributes and allocates the partial print data obtained by dividing the print data into two groups of nozzles by the division means 403 to the two nozzle arrays according to the nozzle drive order in each nozzle array. As a result, partial print data obtained by dividing the print data including the nozzle drive order is distributed and assigned to the two nozzle rows, and ink is ejected from the nozzles of each group based on the assigned partial print data. As a result, as with the comparative example shown in Figure 5, the print resolution can be increased to 1200 dpi, which is twice the drive resolution.

[0040] FIG. 8(a) is a diagram illustrating the positional relationship between the first ink dots A that can be formed by driving the nozzles of the first nozzle array 301 and the ink dots when recording is performed by switching the recording pattern. In the example shown in FIG. 8(a), the numbers 1 to 16 arranged vertically are the same as the numbers 1 to 16 arranged vertically in the comparative example shown in FIG. 5. The black circles in FIG. 8(a) indicate the arrangement of ink dots corresponding to the recording pattern. The shaded areas in FIG. 8(a) indicate the nozzles of the first nozzle array 301 that can form ink dots corresponding to the recording pattern. As described above, the resolution of the recording pattern is 1200 dpi, and the driving resolution is 600 dpi. As shown in FIG. 8(a), the group of nozzles 1 to 8, counting from the end of the first nozzle array 301, is driven in the first half of the driving cycle of the first nozzle array 301. Therefore, the group of nozzles 1 to 8 counting from the end of the first nozzle array 301 forms the first ink dots A, thereby printing pixels to the left of the fifth Lv2 printing pattern K25 and the sixth Lv2 printing pattern K26. The group of nozzles 9 to 16 counting from the end of the first nozzle array 301 is driven in the second half of the drive cycle of the first nozzle array 301. Therefore, the group of nozzles 9 to 16 counting from the end of the first nozzle array 301 forms the first ink dots A, thereby printing pixels to the right of the fifth Lv2 printing pattern K25 and the sixth Lv2 printing pattern K26.

[0041] Furthermore, the group of nozzles 1 to 8 counting from the end of the tenth nozzle array 310 is driven in the second half of the drive cycle of the tenth nozzle array 310. Therefore, the group of nozzles 1 to 8 counting from the end of the tenth nozzle array 310 forms the second ink dots B, thereby printing pixels to the right of the fifth Lv2 recording pattern K25 and the sixth Lv2 recording pattern K26. The group of nozzles 9 to 16 counting from the end of the tenth nozzle array 310 is driven in the first half of the drive cycle of the tenth nozzle array 310. Therefore, the group of nozzles 9 to 16 counting from the end of the tenth nozzle array 310 forms the second ink dots B, thereby printing pixels to the left of the fifth Lv2 recording pattern K25 and the sixth Lv2 recording pattern K26. In this way, in two nozzle rows each having an array of 16 nozzles, partial print data obtained by dividing the print data including the nozzle drive sequence is assigned to the group of nozzles 1 to 8 and the group of nozzles 9 to 16. Then, based on the partial print data assigned to each nozzle group, one of the nozzles in each nozzle group is driven, and an input image is printed using the print pattern.

[0042] FIG. 8(b) is a diagram illustrating the nozzles used in the first nozzle array 301 when switching the print pattern for printing. The left side of FIG. 8(b) shows the first ink dots A formed by the nozzles used in the first nozzle array 301 when switching to print the fifth Level 2 print pattern K25. The right side of FIG. 8(b) shows the first ink dots A formed by the nozzles used in the first nozzle array 301 when switching to print the sixth Level 2 print pattern K26. As shown on the left side of FIG. 8(b), when switching to print the fifth Level 2 print pattern K25, the first, third, fifth, seventh, tenth, twelfth, fourteenth, and sixteenth nozzles, counting from the end of the first nozzle array 301, are used. 8(b), when switching to the sixth Level 2 recording pattern K26 for printing, the nozzles used are the second, fourth, sixth, eighth, ninth, eleventh, thirteenth, and fifteenth, counting from the end of the first nozzle array 301. In this way, by alternately switching between the fifth Level 2 recording pattern K25 and the sixth Level 2 recording pattern K26, it can be seen that the nozzles used in the first nozzle array 301 are made uniform, and the bias in the frequency of nozzle use is reduced.

[0043] FIG. 8(c) is a diagram illustrating the nozzles used in the tenth nozzle array 310 when switching the recording pattern for recording. The left side of FIG. 8(c) shows second ink dots B formed by nozzles used in the tenth nozzle array 310 when switching to the fifth Level 2 recording pattern K25 for recording. The right side of FIG. 8(c) shows second ink dots B formed by nozzles used in the tenth nozzle array 310 when switching to the sixth Level 2 recording pattern K26 for recording. As shown on the left side of FIG. 8(c), when switching to the fifth Level 2 recording pattern K25 for recording, the second, fourth, sixth, eighth, ninth, eleventh, thirteenth, and fifteenth nozzles, counting from the end of the tenth nozzle array 310, are used. 8(c), when switching to the sixth Level 2 recording pattern K26 for printing, the nozzles used are the first, third, fifth, seventh, tenth, twelfth, fourteenth, and sixteenth, counting from the end of the tenth nozzle array 310. In this way, by alternately switching between the fifth Level 2 recording pattern K25 and the sixth Level 2 recording pattern K26, it can be seen that the nozzles used in the tenth nozzle array 310 are made uniform, and the bias in the frequency of nozzle use is reduced.

[0044] 7 and 8, the input image is printed by alternately switching between two types of printing patterns selected from a plurality of types of printing patterns, but the present invention is not limited to this. For example, the input image may be printed by using a printing pattern randomly selected from a plurality of types of printing patterns.

[0045] 7 and 8, a case where ink of the same color is ejected from the nozzles of the first nozzle row 301 and the nozzles of the tenth nozzle row 310 is described, but the present invention is not limited to this. For example, similar recording is performed when ink of the same color is ejected from the nozzles of the second nozzle row 302 and the nozzles of the ninth nozzle row 309, and when ink of the same color is ejected from the nozzles of the third nozzle row 303 and the nozzles of the eighth nozzle row 308. Similar recording is also performed when ink of the same color is ejected from the nozzles of the fourth nozzle row 304 and the nozzles of the seventh nozzle row 307, and when ink of the same color is ejected from the nozzles of the fifth nozzle row 305 and the nozzles of the sixth nozzle row 306.

[0046] Fig. 9 is a diagram illustrating the print pattern and the nozzle drive sequence when printing is performed with a fixed print pattern. Fig. 10 is a diagram illustrating the nozzles used in each nozzle array when printing is performed with a fixed print pattern. In the examples shown in Figs. 9 and 10, M=2 and N=16. Furthermore, the resolution of the input image is 600 dpi, and the drive resolution is 600 dpi.

[0047] FIG. 9(a) is a schematic diagram showing a print pattern for printing an input image at 600 dpi. FIG. 9(b) is a schematic diagram showing the arrangement of dots in the print pattern when printing is performed using a fixed print pattern. The black circles in FIGS. 9(a) and 9(b) indicate the arrangement of dots in the print pattern. When the gradation level of one pixel in the input image is Lv2, one print pattern for printing is selected from pre-prepared Lv2 print patterns, for example, from the six Lv2 print patterns mentioned above. For example, as shown in FIG. 9(a), the fifth Lv2 print pattern K25 is selected. Then, as shown in FIG. 9(b), the input image is printed using the fifth Lv2 print pattern K25 as a fixed pattern.

[0048] FIG. 9(c) is a diagram illustrating the nozzle drive order when printing is performed with a fixed print pattern. FIG. 9(c) shows ink dots when ink of the same color is ejected from the nozzles of the first nozzle row 301 and the nozzles of the tenth nozzle row 310. In the example shown in FIG. 9(c), the numbers 1 to 16 arranged horizontally and the numbers 1 to 16 arranged vertically are the same as the numbers 1 to 16 arranged horizontally and the numbers 1 to 16 arranged vertically in the comparative example shown in FIG. 5. The first ink dots A and the second ink dots B are the same as the first ink dots A and the second ink dots B in the comparative example shown in FIG. 5. The first region CM1 and the second region CM2 are the same as the first region CM1 and the second region CM2 in the comparative example shown in FIG. 5.

[0049] As in the case of switching the print pattern when printing, the nozzle drive order in the tenth nozzle array 310 is shifted by half a period compared to the first nozzle array 301. In the first region CM1, first ink dots A may be formed by the first through eighth nozzles counting from the end of the first nozzle array 301, and second ink dots B may be formed by the ninth through sixteenth nozzles counting from the end of the tenth nozzle array 310. In the second region CM2, first ink dots A may be formed by the ninth through sixteenth nozzles counting from the end of the first nozzle array 301, and second ink dots B may be formed by the first through eighth nozzles counting from the end of the tenth nozzle array 310.

[0050] The setting means 402 of the controller 200 sets the drive order of the 16 drivable nozzles in each nozzle array by shifting the drive cycle by eight nozzles (i.e., by half a cycle) between two nozzle arrays that eject ink of the same color. The dividing means 403 of the controller 200 divides the print data, including the nozzle drive order, into partial print data for the group of nozzles 1 to 8, counting from the end of the nozzle array, and partial print data for the group of nozzles 9 to 16. The allocation means 404 of the controller 200 distributes and allocates the print data divided by the dividing means 403 into two nozzle groups to the two nozzle arrays according to the nozzle drive order in each nozzle array. This allows the print resolution to be 1200 dpi, double the drive resolution, as when printing by switching print patterns.

[0051] FIG. 10(a) illustrates the positional relationship between first ink dots A that can be formed by driving nozzles in the first nozzle array 301 and ink dots when recording is performed with a fixed recording pattern. In the example shown in FIG. 10(a), the numbers 1 to 16 arranged vertically are the same as the numbers 1 to 16 arranged vertically in the comparative example shown in FIG. 5. The black circles in FIG. 10(a) indicate the arrangement of ink dots corresponding to the recording pattern. The shaded areas in FIG. 10(a) indicate nozzles in the first nozzle array 301 that can form ink dots corresponding to the recording pattern. As described above, the resolution of the recording pattern is 1200 dpi, and the driving resolution is 600 dpi. As shown in FIG. 10(a), the group of nozzles 1 to 8, counting from the end of the first nozzle array 301, is driven in the first half of the driving cycle of the first nozzle array 301. Therefore, the group of nozzles 1 to 8 counting from the end of the first nozzle array 301 records pixels on the left side of the fifth Lv2 recording pattern K25 by forming the first ink dots A. The group of nozzles 9 to 16 counting from the end of the first nozzle array 301 is driven in the latter half of the drive cycle of the first nozzle array 301. Therefore, the group of nozzles 9 to 16 counting from the end of the first nozzle array 301 records pixels on the right side of the fifth Lv2 recording pattern K25 by forming the first ink dots A.

[0052] Furthermore, the group of nozzles 1 to 8 counting from the end of the tenth nozzle array 310 is driven in the second half of the drive cycle of the tenth nozzle array 310. Therefore, the group of nozzles 1 to 8 counting from the end of the tenth nozzle array 310 forms the second ink dots B, thereby printing pixels on the right side of the fifth Level 2 printing pattern K25. The group of nozzles 9 to 16 counting from the end of the tenth nozzle array 310 is driven in the first half of the drive cycle of the tenth nozzle array 310. Therefore, the group of nozzles 9 to 16 counting from the end of the tenth nozzle array 310 forms the second ink dots B, thereby printing pixels on the left side of the fifth Level 2 printing pattern K25. In this way, in two nozzle arrays each having 16 nozzles arranged in each array, partial print data obtained by dividing print data including the nozzle drive order is assigned to the group of nozzles 1 to 8 and the group of nozzles 9 to 16. Then, based on the partial print data assigned to each nozzle group, one of the nozzles in each nozzle group is driven, and an input image is printed using the print pattern.

[0053] FIG. 10B is a diagram illustrating the nozzles used in the first nozzle array 301 when printing a fixed print pattern. On the left and right sides of FIG. 10B, first ink dots A corresponding to the nozzles used in the first nozzle array 301 when continuously printing the fifth Level 2 print pattern K25 are shown. As shown in FIG. 10B, when continuously printing the fifth Level 2 print pattern K25, the first, third, fifth, seventh, tenth, twelfth, fourteenth, and sixteenth nozzles, counting from the end of the first nozzle array 301, are used. As such, when printing a fixed print pattern, only half of the 16 nozzles in the first nozzle array 301 are used, which indicates that there is a bias in the frequency of nozzle use in the first nozzle array 301.

[0054] FIG. 10(c) is a diagram illustrating the nozzles used in the tenth nozzle array 310 when printing a fixed print pattern. On the left and right sides of FIG. 10(c), second ink dots B corresponding to the nozzles used in the tenth nozzle array 310 when continuously printing the fifth Level 2 print pattern K25 are shown. As shown in FIG. 10(c), when continuously printing the fifth Level 2 print pattern K25, the second, fourth, sixth, eighth, ninth, eleventh, thirteenth, and fifteenth nozzles, counting from the end of the tenth nozzle array 310, are used. Thus, when printing a fixed print pattern, only half of the 16 nozzles in the tenth nozzle array 310 are used, which indicates a bias in the frequency of nozzle use in the tenth nozzle array 310.

[0055] 9 and 10, a case where ink of the same color is ejected from the nozzles of the first nozzle row 301 and the nozzles of the tenth nozzle row 310 is described, but the present invention is not limited to this. For example, similar recording is performed when ink of the same color is ejected from the nozzles of the second nozzle row 302 and the nozzles of the ninth nozzle row 309, and when ink of the same color is ejected from the nozzles of the third nozzle row 303 and the nozzles of the eighth nozzle row 308. Similar recording is also performed when ink of the same color is ejected from the nozzles of the fourth nozzle row 304 and the nozzles of the seventh nozzle row 307, and when ink of the same color is ejected from the nozzles of the fifth nozzle row 305 and the nozzles of the sixth nozzle row 306.

[0056] The ejection elements (electrothermal conversion elements) provided in the nozzles wear out due to repeated ejection, so if there is a bias in the frequency of nozzle use, it will shorten the life of the print head 101. In this embodiment, a control method will be described that can reduce the bias in the frequency of nozzle use even when printing with a fixed print pattern.

[0057] <Method for controlling a recording device> Next, a control method for the recording device 100 according to the first embodiment will be described. Fig. 11 is a flowchart showing the control method for the recording device 100. Note that the CPU 201 executes a control program stored in the ROM 202 of the controller 200 as a computer, thereby executing each process in the flowchart shown in Fig. 11. When an operation to instruct the start of a recording operation is performed on the start switch 222, the CPU 201 starts each process in the flowchart shown in Fig. 11.

[0058] In step S101, the controller 200 determines whether the number of recorded pages PF is equal to or less than a threshold value P1. The threshold value P1 is set in advance. For example, the threshold value P1 is set based on the number of pages to be recorded, such as 5000 (pages), 10000 (pages), etc. If the number of recorded pages PF is equal to or less than the threshold value P1, i.e., if the determination in step S101 is YES, the process proceeds to step S104. If the number of recorded pages PF is greater than the threshold value P1, i.e., if the determination in step S101 is NO, the process proceeds to step S102.

[0059] In step S102, the change means 405 of the controller 200 changes the allocation of partial print data for the two nozzle arrays according to the nozzle drive order in each nozzle array, and then proceeds to step S103. At this time, the change means 405 changes the nozzles that are driven based on the partial print data when printing is performed using a fixed print pattern, in accordance with changing the allocation of partial print data according to the nozzle drive order in each nozzle array. This makes it possible to reduce bias in the frequency of nozzle use, even when printing is performed using a fixed print pattern. The process of changing the allocation of partial print data for each nozzle array will be described later.

[0060] In step S103, the controller 200 sets the number of recording pages PF to 0, and then the process proceeds to step S104.

[0061] In step S104, the controller 200 adds 1 to the number of print pages PF and proceeds to step S105. By processing steps S101 to S104, the change means 405 of the controller 200 can change the nozzles to be driven based on the partial print data when printing is performed using a fixed print pattern, at a predetermined timing for each page to be printed.

[0062] In step S105, the controller 200 determines, for each pixel of the input image within the same page, whether the pixel to be subjected to the pseudo-halftone processing is an edge pixel. An edge pixel refers to a pixel that is one or several pixels from the outermost pixel among pixels having a gradation level of Lv1 or higher. When a smudge-resistant ink and recording medium are used, the pixel that is one pixel from the outermost pixel can be designated as an edge pixel. When a smudge-prone ink and recording medium are used, good results can be obtained by designating several pixels from the outermost pixel as an edge pixel. Furthermore, pixels having a gradation level of Lv1 or higher, excluding the edge pixel, are referred to as non-edge pixels. If the pixel to be subjected to the pseudo-halftone processing is an edge pixel, i.e., if the determination in step S105 is YES, the process proceeds to step S106. If the pixel to be subjected to the pseudo-halftone processing is a non-edge pixel, i.e., if the determination in step S105 is NO, the process proceeds to step S107.

[0063] In step S106, the selection means 401 of the controller 200 performs pseudo-halftoning on the pixels in the edge portion to determine the gradation of each pixel in the edge portion. Then, the selection means 401 selects a specific (one type of) recording pattern corresponding to the gradation level of the pixels in the edge portion from multiple types of recording patterns prepared in advance, and proceeds to step S108. As a result, the edge portion is recorded with a fixed one type of recording pattern, as exemplified in Figures 9 and 10. The process of selecting the recording pattern corresponding to the gradation level of the pixels in the edge portion will be described later.

[0064] In step S107, the selection means 401 of the controller 200 performs pseudo-halftoning on the pixels in the non-edge portion to determine the gradation of each pixel in the non-edge portion. The selection means 401 then selects one recording pattern from a plurality of pre-prepared recording patterns that corresponds to the gradation level of the pixels in the non-edge portion, and proceeds to step S108. If the gradation level of the pixels in the non-edge portion is one of Lv1, Lv2, and Lv3, the selection means 401 randomly selects one recording pattern from the plurality of recording patterns that corresponds to that gradation level. As a result, the non-edge portion is recorded by sequentially switching the recording patterns, as illustrated in FIGS. 7 and 8. The process of selecting the recording pattern that corresponds to the gradation level of the pixels in the non-edge portion will be described later.

[0065] In step S108, the controller 200 determines whether or not the selection of recording patterns has been completed for all pixels of the input image within the same page. If the selection of recording patterns has not been completed for all pixels within the same page, i.e., if the determination in step S108 is NO, the process returns to step S105, where the determination of whether or not the pixel to be subjected to pseudo-halftoning is an edge portion and the selection of recording patterns are repeated. If the selection of recording patterns has been completed for all pixels within the same page, i.e., if the determination in step S108 is YES, the process proceeds to step S109.

[0066] In step S109, the controller 200 performs a printing process for one page of images by using the printing pattern selected in the previous steps S105 to S107. At this time, the controller 200 performs a printing process for the image of the edge portion by using a fixed printing pattern. The controller 200 performs a printing process for the image of the non-edge portion by switching the printing pattern.

[0067] In the next step S110, the controller 200 determines whether or not the recording process for the images of all pages has been completed. If the recording process for the images of all pages has not been completed, that is, if the determination in step S110 is NO, the process returns to step S101 and proceeds to the recording process for the image of the next page. If the recording process for the images of all pages has been completed, that is, if the determination in step S110 is YES, the process ends.

[0068] Next, a process for selecting a recording pattern corresponding to the gradation level of each pixel of the input image will be described. Fig. 12 is a schematic diagram showing an example of the process for selecting a recording pattern. Fig. 12(a) is a schematic diagram showing the vicinity of an edge portion in the input image IM. Fig. 12(b) is a schematic diagram showing an example in which each pixel of the input image is replaced with a Lv3 recording pattern. Fig. 12(c) is a schematic diagram showing the arrangement of dots in the Lv3 recording pattern that has replaced each pixel of the input image. The black circles in Fig. 12(c) indicate the arrangement of dots in the Lv3 recording pattern.

[0069] First, for ease of explanation, we will explain the case where the gradation level of each pixel in the input image IM is uniform at Lv3, as shown in FIG. 12(a). The pixels in the input image IM include pixels in the edge portion EG and pixels in the non-edge portion NE. The pixels in the edge portion EG shown in FIG. 12(a) are pixels in the portion one pixel from the outermost side among pixels whose gradation level is Lv1 or higher. As shown in FIG. 6(d), the Lv3 recording pattern includes a first Lv3 recording pattern K31, a second Lv3 recording pattern K32, a third Lv3 recording pattern K33, and a fourth Lv3 recording pattern K34.

[0070] 12(b), pixel G3 having a gradation level of Lv3 is replaced with one of four Lv3 recording patterns and recorded on the recording medium MD. For pixels in the non-edge portion NE, one of the first Lv3 recording pattern K31, the second Lv3 recording pattern K32, the third Lv3 recording pattern K33, and the fourth Lv3 recording pattern K34 is randomly selected. In addition, to prevent bias in the recording patterns, the recording patterns are selected so that the first Lv3 recording pattern K31, the second Lv3 recording pattern K32, the third Lv3 recording pattern K33, and the fourth Lv3 recording pattern K34 appear approximately equally. 12(a) to 12(c), for example, the second Lv3 recording pattern K32 is selected for the upper left pixel near the edge portion EG, and the arrangement of dots (of the second Lv3 recording pattern K32) representing the Lv3 gradation level is determined. The fourth Lv3 recording pattern K34 is selected for the second pixel from the upper left near the edge portion EG, and the arrangement of dots (of the fourth Lv3 recording pattern K34) representing the Lv3 gradation level is determined.

[0071] For pixels in the edge portion EG, a specific (one type of) recording pattern is selected from the first Level 3 recording pattern K31, the second Level 3 recording pattern K32, the third Level 3 recording pattern K33, and the fourth Level 3 recording pattern K34. For example, as shown in FIGS. 12(a) to 12(c), for pixels in the right edge portion EG, the first Level 3 recording pattern K31 is fixedly selected, and the arrangement of dots (of the first Level 3 recording pattern K31) representing the Level 3 gradation level is determined. This results in a uniform arrangement of dots in the edge portion EG. The uniform arrangement of dots in the edge portion EG can reduce unevenness in the image of the edge portion EG, thereby improving the quality of the image in the edge portion EG.

[0072] The gradation level of pixels outside the edge portion EG is Lv0. As shown in Figures 12(a) to 12(c), a pixel G0 having a gradation level of Lv0 is replaced with a recording pattern K01 of Lv0 (see Figure 6(a)).

[0073] Next, we will explain the case where the gradation level of each pixel in the input image is uniform at Lv2. FIG. 13 is a schematic diagram showing another example of the process of selecting a recording pattern. FIG. 13(a) is a schematic diagram showing an example in which each pixel in the input image is replaced with a Lv2 recording pattern. FIG. 13(b) is a schematic diagram showing the arrangement of dots in the Lv2 recording pattern that has replaced each pixel in the input image. The black circles in FIG. 13(b) indicate the arrangement of dots in the Lv2 recording pattern. As shown in FIG. 6(c), the Lv2 recording pattern includes a first Lv2 recording pattern K21, a second Lv2 recording pattern K22, and a third Lv2 recording pattern K23. Furthermore, the Lv2 recording pattern includes a fourth Lv2 recording pattern K24, a fifth Lv2 recording pattern K25, and a sixth Lv2 recording pattern K26.

[0074] Pixels having a Lv2 gradation level are replaced with one of six Lv2 recording patterns (K21 to K26) and recorded on the recording medium MD, as shown in FIG. 13(a), for example. For pixels in the non-edge portion NE, one of the six Lv2 recording patterns (K21 to K26) is randomly selected. To prevent bias in the recording patterns, the recording patterns are selected so that the six Lv2 recording patterns (K21 to K26) appear approximately evenly. For example, as shown in FIGS. 13(a) and 13(b), the second Lv2 recording pattern K22 is selected for the upper left pixel near the edge portion EG, and the arrangement of dots (of the second Lv2 recording pattern K22) representing the Lv2 gradation level is determined. For the second pixel from the top left in the vicinity of the edge portion EG, the fourth Lv2 recording pattern K24 is selected, and the arrangement of dots (of the fourth Lv2 recording pattern K24) representing the Lv2 gradation level is determined.

[0075] For pixels in the edge portion EG, a specific (one type) recording pattern is selected from six types of Lv2 recording patterns (K21 to K26). For example, as shown in FIGS. 13(a) and 13(b), for pixels in the right edge portion EG, the fifth Lv2 recording pattern K25 is fixedly selected, and the arrangement of dots (of the fifth Lv2 recording pattern K25) representing the Lv2 gradation level is determined. As described above, the uniform arrangement of dots in the edge portion EG can reduce unevenness in the image of the edge portion EG, thereby improving the quality of the image in the edge portion EG. Furthermore, pixels located outside the edge portion EG (having a Lv0 gradation level) are replaced with the Lv0 recording pattern K01.

[0076] In this embodiment, in addition to a first printing mode that allows printing to be performed using a fixed printing pattern for a portion of the input image (e.g., an edge portion), a second printing mode that does not use a fixed printing pattern may be provided. In the second printing mode, printing is performed using a switching printing pattern for the entire input image. Figure 14 is a schematic diagram showing a modified example of the process of selecting a printing pattern. Figure 14(a) is a schematic diagram showing an example in which each pixel of the input image is replaced with a Level 3 printing pattern. Figure 14(b) is a schematic diagram showing the arrangement of dots of the Level 3 printing pattern that has replaced each pixel of the input image. The black circles in Figure 14(b) indicate the arrangement of dots of the Level 3 printing pattern.

[0077] In the modified example shown in FIGS. 14(a) and 14(b), a case will be described in which the gradation level of each pixel in the input image is uniform at Lv3. In the second recording mode, one of four Lv3 recording patterns (K31 to K34) is randomly selected for pixels in both the edge portion EG and the non-edge portion NE. For example, as shown in FIGS. 14(a) and 14(b), the second Lv3 recording pattern K32 is selected for the upper left pixel near the edge portion EG, and the dot arrangement (of the second Lv3 recording pattern K32) representing the Lv3 gradation level is determined. The fourth Lv3 recording pattern K34 is selected for the uppermost pixel in the edge portion EG, and the dot arrangement (of the fourth Lv3 recording pattern K34) representing the Lv3 gradation level is determined.

[0078] As described above, when a fixed print pattern is used to print the edge portion of an input image, a bias in the frequency of nozzle use occurs. To reduce this bias in the frequency of nozzle use, the change unit 405 of the controller 200 changes the allocation of partial print data according to the nozzle drive order in each nozzle array at a predetermined timing (for example, the timing for each page to be printed).

[0079] Next, the process of changing the allocation of partial print data in each nozzle array will be described. Fig. 15 is a diagram illustrating the print pattern and nozzle drive order when the allocation of partial print data in each nozzle array has been changed. Fig. 16 is a diagram illustrating the nozzles used in each nozzle array when the allocation of partial print data in each nozzle array has been changed. In the examples shown in Figs. 15 and 16, M=2 and N=16, as in the examples shown in Figs. 9 and 10. Furthermore, the resolution of the input image is 600 dpi, and the drive resolution is 600 dpi.

[0080] FIG. 15(a) is a schematic diagram similar to FIG. 9(a) showing a print pattern for printing a 600 dpi input image. FIG. 15(b) is a schematic diagram similar to FIG. 9(b) showing the arrangement of dots in a print pattern when printing is performed with a fixed print pattern. FIG. 15(c) is a diagram illustrating the nozzle drive order when the allocation of partial print data in each nozzle array is changed. FIG. 15(c) shows ink dots when the same color ink is ejected from the nozzles of the first nozzle array 301 and the nozzles of the tenth nozzle array 310. In the example shown in FIG. 15(c), the numbers 1 to 16 arranged horizontally and the numbers 1 to 16 arranged vertically are the same as the numbers 1 to 16 arranged horizontally and the numbers 1 to 16 arranged vertically in the comparative example shown in FIG. 5. The first ink dots A and the second ink dots B are the same as the first ink dots A and the second ink dots B in the comparative example shown in FIG. 5. The first region CM1 and the second region CM2 are similar to the first region CM1 and the second region CM2 in the comparative example shown in FIG.

[0081] In the first nozzle array 301, the first ink dot A can be formed by driving the nozzles in the order of the 9th nozzle, the 10th nozzle, ..., and the 16th nozzle counting from the end, followed by the first nozzle, the second nozzle, ..., and the eighth nozzle. In the tenth nozzle array 310, the second ink dot B can be formed by driving the nozzles in the order of the 1st nozzle, the second nozzle, the third nozzle, the fourth nozzle, ..., and the 16th nozzle counting from the end. Meanwhile, in the example shown in FIG. 9( c), in the first nozzle array 301, the first ink dot A can be formed by driving the nozzles in the order of the 1st nozzle, the second nozzle, the third nozzle, the fourth nozzle, ..., and the 16th nozzle counting from the end. In the tenth nozzle array 310, the second ink dot B can be formed by driving the nozzles in the order of the 9th nozzle, the 10th nozzle, ..., and the 16th nozzle counting from the end.

[0082] The change unit 405 of the controller 200 switches the drive order of the nozzles in the first nozzle row 301 and the drive order of the nozzles in the tenth nozzle row 310. In other words, the change unit 405 switches the allocation of partial print data of the group of nozzles 1 to 8, counting from the end of the nozzle row, and partial print data of the group of nozzles 9 to 16, between the first nozzle row 301 and the tenth nozzle row 310. In this way, the change unit 405 switches the allocation of partial print data according to the drive order of the nozzles in the first nozzle row 301 and the tenth nozzle row 310.

[0083] FIG. 16(a) is a diagram illustrating the positional relationship between first ink dots A that can be formed by driving the nozzles of the first nozzle array 301 and ink dots when recording is performed with a fixed recording pattern. In the example shown in FIG. 16(a), the numbers 1 to 16 arranged vertically are the same as the numbers 1 to 16 arranged vertically in the comparative example shown in FIG. 5. The black circles in FIG. 16(a) indicate the arrangement of ink dots corresponding to the recording pattern. The shaded areas in FIG. 16(a) indicate nozzles in the first nozzle array 301 that can form ink dots corresponding to the recording pattern.

[0084] As described above, the change unit 405 swaps the allocation of partial print data for the group of nozzles 1 to 8, counting from the end of the nozzle array, with partial print data for the group of nozzles 9 to 16, between the first nozzle array 301 and the tenth nozzle array 310. When the partial print data allocated to the first nozzle array 301 and the tenth nozzle array 310 is swapped, the group of nozzles 1 to 8, counting from the end of the first nozzle array 301, is driven in the second half of the drive cycle of the first nozzle array 301. Therefore, as shown in FIG. 16(a), the group of nozzles 1 to 8, counting from the end of the first nozzle array 301, forms the first ink dot A, thereby recording pixels on the right side of the fifth Level 2 print pattern K25. The group of nozzles 9 to 16, counting from the end of the first nozzle array 301, is driven in the first half of the drive cycle of the first nozzle array 301. Therefore, the group of nozzles 9th to 16th counting from the end of the first nozzle row 301 forms the first ink dots A, thereby printing the pixels on the left side of the fifth Lv2 printing pattern K25.

[0085] Furthermore, the group of nozzles 1 to 8 counting from the end of the tenth nozzle array 310 is driven in the first half of the drive cycle of the tenth nozzle array 310. Therefore, the group of nozzles 1 to 8 counting from the end of the tenth nozzle array 310 forms the second ink dots B, thereby recording pixels on the left side of the fifth Lv2 recording pattern K25. The group of nozzles 9 to 16 counting from the end of the tenth nozzle array 310 is driven in the second half of the drive cycle of the tenth nozzle array 310. Therefore, the group of nozzles 9 to 16 counting from the end of the tenth nozzle array 310 forms the second ink dots B, thereby recording pixels on the right side of the fifth Lv2 recording pattern K25.

[0086] FIG. 16(b) is a diagram illustrating the nozzles used in the first nozzle array 301 when the allocation of partial print data in each nozzle array is changed. On the left and right sides of FIG. 16(b), first ink dots A corresponding to the nozzles used in the first nozzle array 301 when continuously printing the fifth Level 2 print pattern K25 are shown. As shown in FIG. 16(b), when continuously printing the fifth Level 2 print pattern K25, the second, fourth, sixth, eighth, ninth, eleventh, thirteenth, and fifteenth nozzles, counting from the end of the first nozzle array 301, are used. On the other hand, in the example shown in FIG. 10(b), when continuously printing the fifth Level 2 print pattern K25, the first, third, fifth, seventh, tenth, twelfth, fourteenth, and sixteenth nozzles, counting from the end of the first nozzle array 301, are used. 16(b) with the example shown in Fig. 10(b), it can be seen that the fifth Level 2 recording pattern K25 for recording remains unchanged, but the nozzles used in the first nozzle row 301 are changed. By swapping the allocation of partial recording data according to the nozzle drive order in the first nozzle row 301 and the tenth nozzle row 310, the nozzles used in the first nozzle row 301 are made uniform, and bias in the frequency of nozzle use is reduced.

[0087] FIG. 16(c) is a diagram illustrating the nozzles used in the tenth nozzle array 310 when the allocation of partial print data in each nozzle array is changed. On the left and right sides of FIG. 16(c), second ink dots B corresponding to the nozzles used in the tenth nozzle array 310 when continuously printing the fifth Level 2 print pattern K25 are shown. As shown in FIG. 16(c), when continuously printing the fifth Level 2 print pattern K25, the first, third, fifth, seventh, tenth, twelfth, fourteenth, and sixteenth nozzles, counting from the end of the tenth nozzle array 310, are used. Meanwhile, in the example shown in FIG. 10(c), when continuously printing the fifth Level 2 print pattern K25, the second, fourth, sixth, eighth, ninth, eleventh, thirteenth, and fifteenth nozzles, counting from the end of the tenth nozzle array 310, are used. 16(c) with the example shown in Fig. 10(c), it can be seen that the fifth Level 2 recording pattern K25 for recording remains unchanged, but the nozzles used in the tenth nozzle row 310 are changed. By swapping the allocation of partial recording data according to the nozzle drive order in the first nozzle row 301 and the tenth nozzle row 310, the nozzles used in the tenth nozzle row 310 are made uniform, and imbalances in the frequency of nozzle use are reduced.

[0088] 15 and 16, a case where ink of the same color is ejected from the nozzles of the first nozzle row 301 and the nozzles of the tenth nozzle row 310 is described, but the present invention is not limited to this. For example, similar recording is performed when ink of the same color is ejected from the nozzles of the second nozzle row 302 and the nozzles of the ninth nozzle row 309, and when ink of the same color is ejected from the nozzles of the third nozzle row 303 and the nozzles of the eighth nozzle row 308. Similar recording is also performed when ink of the same color is ejected from the nozzles of the fourth nozzle row 304 and the nozzles of the seventh nozzle row 307, and when ink of the same color is ejected from the nozzles of the fifth nozzle row 305 and the nozzles of the sixth nozzle row 306. Black ink is also ejected from the nozzles of the fourth to seventh nozzle rows 304 to 307. For example, two sets of two nozzle arrays may be used, each set consisting of two nozzle arrays, the fourth nozzle array 304 and the seventh nozzle array 307, and two nozzle arrays, the fifth nozzle array 305 and the sixth nozzle array 306. The two nozzle arrays, the fourth nozzle array 304 and the seventh nozzle array 307, and the two nozzle arrays, the fifth nozzle array 305 and the sixth nozzle array 306, may be alternately switched and used at a predetermined timing for each page to be printed. This makes it possible to further reduce bias in the frequency of use of the nozzles used in the fourth to seventh nozzle arrays 304 to 307. Alternatively, as described in the third embodiment, a set of four nozzle arrays, the fourth to seventh nozzle arrays 304 to 307, may be used.

[0089] In this embodiment, when printing is performed using a fixed print pattern, the modification unit 405 modifies the allocation of partial print data according to the nozzle drive order in each of the two nozzle arrays. For example, the modification unit 405 changes the nozzles driven based on the partial print data to other nozzles in the two nozzle arrays in response to changing the allocation of partial print data according to the nozzle drive order in each of the two nozzle arrays. As a specific example, the modification unit 405 swaps the allocation of partial print data for the group of nozzles 1 to 8, counting from the end of the nozzle array, with the allocation of partial print data for the group of nozzles 9 to 16, between the first nozzle array 301 and the tenth nozzle array 310. This standardizes the nozzles used in each nozzle array, reducing unevenness in the frequency of nozzle use. As such, this embodiment can reduce unevenness in the frequency of nozzle use when applying pseudo-halftoning to an inkjet printing device.

[0090] Furthermore, the change unit 405 changes the allocation of partial print data according to the nozzle drive order in each of the two nozzle arrays at a predetermined timing for each page to be printed. In this case, the predetermined timing is set based on the number of pages to be printed (the aforementioned threshold P1). This makes it possible to reduce bias in the frequency of nozzle use while maintaining the printing speed and print quality.

[0091] <<Second embodiment>> Next, a second embodiment will be described. Since the individual components in the second embodiment have the same configuration as those in the first embodiment, they will be described using the same reference numerals as those in the first embodiment.

[0092] <Method for controlling a recording device> A control method for the recording apparatus 100 according to the second embodiment will now be described. In the second embodiment, the controller 200 performs the same processing as in the first embodiment, except for the processing in step S102. In step S102, the change means 405 of the controller 200 changes the recording pattern to be selected from among multiple recording patterns when recording is performed using a fixed recording pattern, and the process proceeds to step S103. At this time, the change means 405 changes the nozzles to be driven based on partial recording data when recording is performed using a fixed recording pattern, in accordance with the change in the recording pattern selected by the selection means 401 (see also the two-dot chain line in FIG. 4). This makes it possible to reduce bias in the frequency of nozzle use, even when recording is performed using a fixed recording pattern.

[0093] Next, we will explain the process of changing the print pattern selected when printing is performed using a fixed print pattern. Fig. 17 is a diagram explaining the print pattern and the nozzle drive order when the print pattern is changed. Fig. 18 is a diagram explaining the nozzles used in each nozzle array when the print pattern is changed. In the examples shown in Figs. 17 and 18, M=2 and N=16, as in the examples shown in Figs. 9 and 10. Furthermore, the resolution of the input image is 600 dpi, and the drive resolution is 600 dpi.

[0094] FIG. 17(a) is a schematic diagram showing a changed recording pattern. FIG. 17(b) is a schematic diagram showing the dot arrangement of the recording pattern when the recording pattern is changed. The black circles in FIGS. 17(a) and 17(b) indicate the dot arrangement of the changed recording pattern. The change means 405 of the controller 200 changes the recording pattern selected when recording is performed using a fixed recording pattern from the fifth Level 2 recording pattern K25 to the sixth Level 2 recording pattern K26, as shown in FIG. 17(a), for example. In this way, one recording pattern different from the recording pattern selected in step S106 is selected from among the prepared Level 2 recording patterns, for example, the six Level 2 recording patterns mentioned above. Then, as shown in FIG. 17(b), the input image is recorded using the sixth Level 2 recording pattern K26, which is a fixed version of the fifth Level 2 recording pattern K25.

[0095] The fifth Level 2 recording pattern K25 is a houndstooth dot pattern in which dots are arranged in the upper left pixel and lower right pixel of Fig. 9(a). The sixth Level 2 recording pattern K26 is a houndstooth dot pattern in which dots are arranged in the upper right pixel and lower left pixel of Fig. 17(a), in the opposite direction to the fifth Level 2 recording pattern K25. Fig. 17(c) is a diagram similar to Fig. 9(c) that explains the nozzle drive order when the recording pattern is changed.

[0096] FIG. 18(a) is a diagram illustrating the positional relationship between first ink dots A that can be formed by driving the nozzles of the first nozzle row 301 and ink dots when the recording pattern is changed. In the example shown in FIG. 18(a), the numbers 1 to 16 arranged vertically are the same as the numbers 1 to 16 arranged vertically in the comparative example shown in FIG. 5. The black circles in FIG. 18(a) indicate the arrangement of ink dots corresponding to the recording pattern. The shaded areas in FIG. 18(a) indicate the nozzles of the first nozzle row 301 that can form ink dots corresponding to the recording pattern.

[0097] As described above, the change unit 405 changes the print pattern selected when printing is performed using a fixed print pattern from the fifth Level 2 print pattern K25 to the sixth Level 2 print pattern K26. Note that the change unit 405 does not interchange the print data assigned to the first nozzle array 301 and the tenth nozzle array 310. Therefore, as shown in FIG. 18(a), the group of nozzles 1 to 8 counting from the end of the first nozzle array 301 prints pixels to the left of the sixth Level 2 print pattern K26 by forming the first ink dots A. The group of nozzles 9 to 16 counting from the end of the first nozzle array 301 prints pixels to the right of the sixth Level 2 print pattern K26 by forming the first ink dots A.

[0098] Additionally, the group of nozzles 1 to 8 counting from the end of the tenth nozzle array 310 prints pixels on the right side of the sixth Level 2 recording pattern K26 by forming second ink dots B. The group of nozzles 9 to 16 counting from the end of the tenth nozzle array 310 prints pixels on the left side of the sixth Level 2 recording pattern K26 by forming second ink dots B.

[0099] FIG. 18(b) is a diagram illustrating the nozzles used in the first nozzle array 301 when the recording pattern is changed. On the left and right sides of FIG. 18(b), first ink dots A corresponding to the nozzles used in the first nozzle array 301 when continuously recording the sixth Level 2 recording pattern K26 are shown. As shown in FIG. 18(b), when continuously recording the sixth Level 2 recording pattern K26, the second, fourth, sixth, eighth, ninth, eleventh, thirteenth, and fifteenth nozzles, counting from the end of the first nozzle array 301, are used. On the other hand, in the example shown in FIG. 10(b), when continuously recording the fifth Level 2 recording pattern K25, the first, third, fifth, seventh, tenth, twelfth, fourteenth, and sixteenth nozzles, counting from the end of the first nozzle array 301, are used. 18(b) with the example shown in Fig. 10(b), it can be seen that there is a change in the nozzles used in the first nozzle row 301. By changing the print pattern selected from multiple print patterns when printing is performed using a fixed print pattern, the nozzles used in the first nozzle row 301 are made uniform, and bias in the frequency of nozzle use is reduced.

[0100] FIG. 18(c) is a diagram illustrating the nozzles used in the tenth nozzle array 310 when the recording pattern is changed. On the left and right sides of FIG. 18(c), second ink dots B corresponding to the nozzles used in the tenth nozzle array 310 when continuously recording the sixth Level 2 recording pattern K26 are shown. As shown in FIG. 18(c), when continuously recording the sixth Level 2 recording pattern K26, the first, third, fifth, seventh, tenth, twelfth, fourteenth, and sixteenth nozzles, counting from the end of the tenth nozzle array 310, are used. On the other hand, in the example shown in FIG. 10(c), when continuously recording the fifth Level 2 recording pattern K25, the second, fourth, sixth, eighth, ninth, eleventh, thirteenth, and fifteenth nozzles, counting from the end of the tenth nozzle array 310, are used. Comparing the example shown in Figure 18(c) with the example shown in Figure 10(c), it can be seen that there is a change in the nozzles used in the tenth nozzle row 310. By changing the recording pattern selected from multiple types of recording patterns when recording is performed using a fixed recording pattern, the nozzles used in the tenth nozzle row 310 are made uniform, and bias in the frequency of nozzle use is reduced.

[0101] 17 and 18, a case where ink of the same color is ejected from the nozzles of the first nozzle row 301 and the nozzles of the tenth nozzle row 310 is described, but the present invention is not limited to this. For example, similar recording is performed when ink of the same color is ejected from the nozzles of the second nozzle row 302 and the nozzles of the ninth nozzle row 309, and when ink of the same color is ejected from the nozzles of the third nozzle row 303 and the nozzles of the eighth nozzle row 308. Similar recording is also performed when ink of the same color is ejected from the nozzles of the fourth nozzle row 304 and the nozzles of the seventh nozzle row 307, and when ink of the same color is ejected from the nozzles of the fifth nozzle row 305 and the nozzles of the sixth nozzle row 306. Black ink is also ejected from the nozzles of the fourth to seventh nozzle rows 304 to 307. For example, two sets of two nozzle arrays may be used, each set consisting of two nozzle arrays, the fourth nozzle array 304 and the seventh nozzle array 307, and the fifth nozzle array 305 and the sixth nozzle array 306. The two nozzle arrays, the fourth nozzle array 304 and the seventh nozzle array 307, and the two nozzle arrays, the fifth nozzle array 305 and the sixth nozzle array 306, may be alternately switched and used at a predetermined timing for each page to be printed. This makes it possible to further reduce bias in the frequency of use of the nozzles used in the fourth to seventh nozzle arrays 304 to 307. Alternatively, as described in the fourth embodiment, a set of four nozzle arrays, the fourth to seventh nozzle arrays 304 to 307, may be used.

[0102] In the second embodiment, the change unit 405 changes the print pattern selected from among multiple print patterns when printing is performed using a fixed print pattern. Specifically, the change unit 405 changes the nozzles driven based on partial print data to other nozzles in the two nozzle arrays in response to changing the print pattern selected from among multiple print patterns. As a specific example, the change unit 405 changes the print pattern selected when printing is performed using a fixed print pattern from the fifth level 2 print pattern K25 to the sixth level 2 print pattern K26. This standardizes the nozzles used in each nozzle array, reducing unevenness in the frequency of nozzle use. Thus, according to the second embodiment, as with the first embodiment, unevenness in the frequency of nozzle use can be reduced when applying pseudo-halftoning to an inkjet printing apparatus.

[0103] As in the first embodiment, the change unit 405 changes the print pattern selected from multiple print patterns when printing is performed using a fixed print pattern at a predetermined timing for each page to be printed. This makes it possible to reduce bias in the frequency of nozzle use while maintaining the print speed and print quality.

[0104] <<Third Embodiment>> Next, a third embodiment will be described. Since the individual components in the third embodiment have the same configuration as those in the first embodiment, they will be described using the same reference numerals as those in the first embodiment.

[0105] <Method for controlling a recording device> A control method for the recording apparatus 100 according to the third embodiment will be described. In the third embodiment, the controller 200 performs the same processing as in the first embodiment, except that recording is performed using four rows of nozzles (fourth to seventh nozzle rows 304 to 307) that eject ink of the same color. Note that in the third embodiment, the pixels in the edge portion are defined as the two outermost pixels among the pixels whose gradation level is Lv1 or higher.

[0106] Fig. 19 is a diagram illustrating the print pattern and the nozzle drive order when printing is performed with a fixed print pattern. Fig. 20 is a diagram illustrating the nozzles used in each nozzle array when printing is performed with a fixed print pattern. In the examples shown in Figs. 19 and 20, M=4 and N=16. Furthermore, the resolution of the input image is 600 dpi, and the drive resolution is 300 dpi.

[0107] FIG. 19(a) is a schematic diagram showing a print pattern for printing an input image at 600 dpi. FIG. 19(b) is a schematic diagram showing the arrangement of dots in the print pattern when printing is performed using a fixed print pattern. The black circles in FIGS. 19(a) and 19(b) indicate the arrangement of dots in the print pattern. When the gradation level of one pixel in the input image is Lv2, one print pattern for printing is selected from pre-prepared Lv2 print patterns, for example, from the six Lv2 print patterns mentioned above. For example, as shown in FIG. 19(a), the fifth Lv2 print pattern K25 is selected. Then, as shown in FIG. 19(b), the input image is printed using the fifth Lv2 print pattern K25 as a fixed pattern.

[0108] Figure 19(c) is a diagram illustrating the nozzle drive order when printing is performed with a fixed print pattern. Figure 19(c) shows ink dots when ink of the same color is ejected from the nozzles of the fourth nozzle row 304, the nozzles of the fifth nozzle row 305, the nozzles of the sixth nozzle row 306, and the nozzles of the seventh nozzle row 307. In the example shown in Figure 19(c), the numbers 1 to 16 arranged horizontally and the numbers 1 to 16 arranged vertically are the same as the numbers 1 to 16 arranged horizontally and the numbers 1 to 16 arranged vertically in the comparative example shown in Figure 5.

[0109] In the third embodiment, an ink dot that can be formed on the recording medium MD by driving the nozzles of the fourth nozzle array 304 is referred to as a first ink dot A. An ink dot that can be formed on the recording medium MD by driving the nozzles of the fifth nozzle array 305 is referred to as a second ink dot B. An ink dot that can be formed on the recording medium MD by driving the nozzles of the sixth nozzle array 306 is referred to as a third ink dot C. An ink dot that can be formed on the recording medium MD by driving the nozzles of the seventh nozzle array 307 is referred to as a fourth ink dot D. For example, the first ink dot A located in the first row and first column indicates an ink dot that can be formed by first driving the first nozzle counting from the end of the fourth nozzle array 304. The second ink dot B located in the first row and first column indicates an ink dot that can be formed by first driving the fifth nozzle counting from the end of the fifth nozzle array 305. The third ink dot C, located in the ninth row and first column, indicates an ink dot that can be formed by first driving the ninth nozzle, counting from the end of the sixth nozzle array 306. The fourth ink dot D, located in the thirteenth row and first column, indicates an ink dot that can be formed by first driving the thirteenth nozzle, counting from the end of the seventh nozzle array 307. The nozzle drive order is controlled so that the ink dots ejected from the earliest nozzle in the drive order in each nozzle group of each nozzle array are aligned in a direction perpendicular to the main scanning direction on the recording medium MD. When the same color ink is ejected from the nozzles of the fourth to seventh nozzle arrays 304 to 307, the color and shape of the second ink dot B, the third ink dot C, and the fourth ink dot D will be the same as the color and shape of the first ink dot A.

[0110] As shown in FIG. 19( c), in the fourth nozzle array 304, a first ink dot A can be formed by driving the nozzles in the order of the first, second, third, fourth, ..., and sixteenth nozzles counting from the end. In the fifth nozzle array 305, a second ink dot B can be formed by driving the nozzles in the order of the fifth, sixth, ..., and sixteenth nozzles counting from the end, and then driving the nozzles in the order of the first, second, ..., and fourth nozzles. In this way, the nozzle driving order in the fifth nozzle array 305 is shifted by a quarter of a cycle compared to the fourth nozzle array 304. In the sixth nozzle array 306, a third ink dot C can be formed by driving the nozzles in the order of the ninth, tenth, ..., and sixteenth nozzles counting from the end, and then driving the nozzles in the order of the first, second, ..., and eighth nozzles. In this way, the nozzle drive order in the sixth nozzle array 306 is shifted by ½ period compared to the fourth nozzle array 304. In the seventh nozzle array 307, the nozzles are driven in the order of the 13th nozzle, the 14th nozzle, ..., and the 16th nozzle counting from the end, and then the nozzles are driven in the order of the 1st nozzle, the 2nd nozzle, ..., and the 12th nozzle, thereby forming the fourth ink dot D. In this way, the nozzle drive order in the seventh nozzle array 307 is shifted by ¾ period compared to the fourth nozzle array 304.

[0111] In the third embodiment, the region in which ink dots are formed by the first through fourth driven nozzles in each nozzle row is referred to as the first region CM1. The region in which ink dots are formed by the fifth through eighth driven nozzles in each nozzle row is referred to as the second region CM2. The region in which ink dots are formed by the ninth through twelfth driven nozzles in each nozzle row is referred to as the third region CM3. The region in which ink dots are formed by the thirteenth through sixteenth driven nozzles in each nozzle row is referred to as the fourth region CM4.

[0112] In the first region CM1, a first ink dot A may be formed by the first to fourth nozzles counting from the end in the fourth nozzle row 304, and a second ink dot B may be formed by the fifth to eighth nozzles counting from the end in the fifth nozzle row 305. In the first region CM1, a third ink dot C may be formed by the ninth to twelfth nozzles counting from the end in the sixth nozzle row 306, and a fourth ink dot D may be formed by the thirteenth to sixteenth nozzles counting from the end in the seventh nozzle row 307.

[0113] In the second region CM2, a first ink dot A may be formed by the fifth to eighth nozzles counting from the end in the fourth nozzle row 304, and a second ink dot B may be formed by the ninth to twelfth nozzles counting from the end in the fifth nozzle row 305. In the second region CM2, a third ink dot C may be formed by the thirteenth to sixteenth nozzles counting from the end in the sixth nozzle row 306, and a fourth ink dot D may be formed by the first to fourth nozzles counting from the end in the seventh nozzle row 307.

[0114] In the third region CM3, a first ink dot A may be formed by the ninth to twelfth nozzles counting from the end of the fourth nozzle row 304, and a second ink dot B may be formed by the thirteenth to sixteenth nozzles counting from the end of the fifth nozzle row 305. In the third region CM3, a third ink dot C may be formed by the first to fourth nozzles counting from the end of the sixth nozzle row 306, and a fourth ink dot D may be formed by the fifth to eighth nozzles counting from the end of the seventh nozzle row 307.

[0115] In the fourth region CM4, a first ink dot A may be formed by the thirteenth to sixteenth nozzles counting from the end in the fourth nozzle row 304, and a second ink dot B may be formed by the first to fourth nozzles counting from the end in the fifth nozzle row 305. In the fourth region CM4, a third ink dot C may be formed by the fifth to eighth nozzles counting from the end in the sixth nozzle row 306, and a fourth ink dot D may be formed by the ninth to twelfth nozzles counting from the end in the seventh nozzle row 307.

[0116] In the third embodiment, the setting means 402 of the controller 200 sets the drive order of the 16 drivable nozzles in each nozzle array by shifting the drive cycle by four nozzles (i.e., by 1 / 4 cycle) between four nozzle arrays that eject ink of the same color. Specifically, the setting means 402 sets the drive order of the nozzles in the fourth nozzle array 304 to the drive order of the first to sixteenth nozzles counting from the end of the fourth nozzle array 304. The setting means 402 sets the drive order of the nozzles in the fifth nozzle array 305 to the drive order of the fifth to sixteenth nozzles and the first to fourth nozzles counting from the end of the fifth nozzle array 305. The setting means 402 sets the drive order of the nozzles in the sixth nozzle array 306 to the drive order of the ninth to sixteenth nozzles and the first to eighth nozzles counting from the end of the sixth nozzle array 306. The setting means 402 sets the nozzle drive order in the seventh nozzle array 307 to the 13th to 16th nozzles and the 1st to 12th nozzles, counting from the end of the seventh nozzle array 307. The dividing means 403 of the controller 200 divides the print data, including the nozzle drive order, into four groups of nozzles, each of which is obtained by shifting the drive order of the 16 nozzles by four. The dividing means 403 divides the print data into partial print data, each of which is the group of nozzles 1 to 4, the group of nozzles 5 to 8, the group of nozzles 9 to 12, and the group of nozzles 13 to 16, counting from the end of the nozzle array. The allocation means 404 of the controller 200 distributes and allocates the partial print data obtained by dividing the print data into four groups of nozzles by the dividing means 403 to the four nozzle arrays according to the nozzle drive order in each nozzle array.

[0117] For example, when forming ink dots in the first region CM1, the allocation unit 404 allocates partial print data of the group of nozzles that are the first to fourth, counting from the end of the nozzle array, to the fourth nozzle array 304. The allocation unit 404 allocates partial print data of the group of nozzles that are the fifth to eighth, counting from the end of the nozzle array, to the fifth nozzle array 305. The allocation unit 404 allocates partial print data of the group of nozzles that are the ninth to twelfth, counting from the end of the nozzle array, to the sixth nozzle array 306. The allocation unit 404 allocates partial print data of the group of nozzles that are the thirteenth to sixteenth, counting from the end of the nozzle array, to the seventh nozzle array 307.

[0118] When forming ink dots in the second region CM2, the allocation unit 404 allocates partial print data of the group of nozzles that are fifth to eighth, counting from the end of the nozzle array, to the fourth nozzle array 304. The allocation unit 404 allocates partial print data of the group of nozzles that are ninth to twelfth, counting from the end of the nozzle array, to the fifth nozzle array 305. The allocation unit 404 allocates partial print data of the group of nozzles that are thirteenth to sixteenth, counting from the end of the nozzle array, to the sixth nozzle array 306. The allocation unit 404 allocates partial print data of the group of nozzles that are first to fourth, counting from the end of the nozzle array, to the seventh nozzle array 307.

[0119] When forming ink dots in the third region CM3, the allocation unit 404 allocates partial print data for the group of nozzles that are 9th to 12th, counting from the end of the nozzle array, to the fourth nozzle array 304. The allocation unit 404 allocates partial print data for the group of nozzles that are 13th to 16th, counting from the end of the nozzle array, to the fifth nozzle array 305. The allocation unit 404 allocates partial print data for the group of nozzles that are 1st to 4th, counting from the end of the nozzle array, to the sixth nozzle array 306. The allocation unit 404 allocates partial print data for the group of nozzles that are 5th to 8th, counting from the end of the nozzle array, to the seventh nozzle array 307.

[0120] When forming ink dots in the fourth region CM4, the allocation unit 404 allocates partial print data for the group of nozzles that are 13 to 16, counting from the end of the nozzle array, to the fourth nozzle array 304. The allocation unit 404 allocates partial print data for the group of nozzles that are 1 to 4, counting from the end of the nozzle array, to the fifth nozzle array 305. The allocation unit 404 allocates partial print data for the group of nozzles that are 5 to 8, counting from the end of the nozzle array, to the sixth nozzle array 306. The allocation unit 404 allocates partial print data for the group of nozzles that are 9 to 12, counting from the end of the nozzle array, to the seventh nozzle array 307. In this way, partial print data obtained by dividing the print data including the nozzle drive order is distributed and allocated to the four nozzle arrays, and ink is ejected from the nozzles of each group based on the allocated partial print data.

[0121] Here, the density in the main scanning direction of the first ink dots A (or the second ink dots B, third ink dots C, and fourth ink dots D) formed per drive cycle is referred to as the drive resolution. The density of the ink dots including the first ink dots A, second ink dots B, third ink dots C, and fourth ink dots D is referred to as the print resolution. According to the third embodiment, if the drive resolution is 300 dpi, the print resolution can be increased to 1200 dpi, which is four times the drive resolution. Therefore, by setting the drive resolution to 300 dpi, which is one-quarter of the print resolution, the movement speed of the carriage 106 in the main scanning direction can be increased, and the print speed can be increased. Furthermore, by setting the print resolution to 1200 dpi, which is four times the drive resolution, the print resolution can be increased, and print quality can be improved.

[0122] FIG. 20(a) illustrates the positional relationship between the first ink dots A that can be formed by driving the nozzles of the fourth nozzle array 304 and the ink dots when recording is performed with a fixed recording pattern. In the example shown in FIG. 20(a), the numbers 1 to 16 arranged vertically are the same as the numbers 1 to 16 arranged vertically in the comparative example shown in FIG. 5. The black circles in FIG. 20(a) indicate the arrangement of ink dots corresponding to the recording pattern. The shaded areas in FIG. 20(a) indicate the nozzles of the fourth nozzle array 304 that can form ink dots corresponding to the recording pattern. As described above, the resolution of the recording pattern is 1200 dpi, and the drive resolution is 300 dpi. As shown in FIG. 20(a), the group of nozzles first through fourth, counting from the end of the fourth nozzle array 304, is driven in the first quarter of the drive cycle of the fourth nozzle array 304. Therefore, the group of nozzles 1 to 4 counting from the end of the fourth nozzle array 304 forms the first ink dots A, thereby recording pixels on the left side of the fifth Level 2 recording pattern K25. The group of nozzles 5 to 8 counting from the end of the fourth nozzle array 304 is driven in the second quarter of the drive cycle of the fourth nozzle array 304. Therefore, the group of nozzles 5 to 8 counting from the end of the fourth nozzle array 304 forms the first ink dots A, thereby recording pixels on the right side of the fifth Level 2 recording pattern K25. The group of nozzles 9 to 12 counting from the end of the fourth nozzle array 304 is driven in the third quarter of the drive cycle of the fourth nozzle array 304. Therefore, the group of nozzles 9 to 12 counting from the end of the fourth nozzle array 304 forms the first ink dots A, thereby recording pixels on the left side of the fifth Level 2 recording pattern K25. The group of nozzles 13 to 16 counting from the end of the fourth nozzle array 304 is driven in the fourth quarter of the drive cycle of the fourth nozzle array 304. Therefore, the group of nozzles 13 to 16 counting from the end of the fourth nozzle array 304 forms the first ink dots A, thereby recording the pixels on the right side of the fifth Lv2 recording pattern K25.

[0123] Furthermore, the group of nozzles 1 to 4 counting from the end of the fifth nozzle array 305 is driven in the fourth quarter of the drive cycle of the fifth nozzle array 305. Therefore, the group of nozzles 1 to 4 counting from the end of the fifth nozzle array 305 forms the second ink dots B, thereby recording pixels on the right side of the fifth Lv2 recording pattern K25. The group of nozzles 5 to 8 counting from the end of the fifth nozzle array 305 is driven in the first quarter of the drive cycle of the fifth nozzle array 305. Therefore, the group of nozzles 5 to 8 counting from the end of the fifth nozzle array 305 forms the second ink dots B, thereby recording pixels on the left side of the fifth Lv2 recording pattern K25. The group of nozzles 9 to 12 counting from the end of the fifth nozzle array 305 is driven in the second quarter of the drive cycle of the fifth nozzle array 305. Therefore, the group of nozzles 9 to 12 counting from the end of the fifth nozzle array 305 records pixels on the right side of the fifth Level 2 recording pattern K25 by forming the second ink dots B. The group of nozzles 13 to 16 counting from the end of the fifth nozzle array 305 is driven in the third quarter of the drive cycle of the fifth nozzle array 305. Therefore, the group of nozzles 13 to 16 counting from the end of the fifth nozzle array 305 records pixels on the left side of the fifth Level 2 recording pattern K25 by forming the second ink dots B.

[0124] The group of nozzles 1 to 4 counting from the end of the sixth nozzle array 306 is driven in the third quarter of the drive cycle of the sixth nozzle array 306. Therefore, the group of nozzles 1 to 4 counting from the end of the sixth nozzle array 306 forms the third ink dot C, thereby recording pixels on the left side of the fifth Level 2 recording pattern K25. The group of nozzles 5 to 8 counting from the end of the sixth nozzle array 306 is driven in the fourth quarter of the drive cycle of the sixth nozzle array 306. Therefore, the group of nozzles 5 to 8 counting from the end of the sixth nozzle array 306 forms the third ink dot C, thereby recording pixels on the right side of the fifth Level 2 recording pattern K25. The group of nozzles 9 to 12 counting from the end of the sixth nozzle array 306 is driven in the first quarter of the drive cycle of the sixth nozzle array 306. Therefore, the group of nozzles 9 to 12 counting from the end of the fourth nozzle array 304 prints pixels on the left side of the fifth Level 2 recording pattern K25 by forming the third ink dots C. The group of nozzles 13 to 16 counting from the end of the sixth nozzle array 306 is driven in the second quarter of the drive cycle of the sixth nozzle array 306. Therefore, the group of nozzles 13 to 16 counting from the end of the sixth nozzle array 306 prints pixels on the right side of the fifth Level 2 recording pattern K25 by forming the third ink dots C.

[0125] The group of nozzles 1 to 4 counting from the end of the seventh nozzle array 307 is driven in the second quarter of the drive cycle of the seventh nozzle array 307. Therefore, the group of nozzles 1 to 4 counting from the end of the seventh nozzle array 307 forms the fourth ink dot D, thereby recording pixels on the right side of the fifth Level 2 recording pattern K25. The group of nozzles 5 to 8 counting from the end of the seventh nozzle array 307 is driven in the third quarter of the drive cycle of the seventh nozzle array 307. Therefore, the group of nozzles 5 to 8 counting from the end of the seventh nozzle array 307 forms the fourth ink dot D, thereby recording pixels on the left side of the fifth Level 2 recording pattern K25. The group of nozzles 9 to 12 counting from the end of the seventh nozzle array 307 is driven in the fourth quarter of the drive cycle of the seventh nozzle array 307. Therefore, the group of nozzles 9 to 12 counting from the end of the seventh nozzle array 307 forms the fourth ink dots D, thereby printing pixels on the right side of the fifth Level 2 printing pattern K25. The group of nozzles 13 to 16 counting from the end of the seventh nozzle array 307 is driven in the first quarter of the drive cycle of the seventh nozzle array 307. Therefore, the group of nozzles 13 to 16 counting from the end of the seventh nozzle array 307 prints pixels on the left side of the fifth Level 2 printing pattern K25 by forming the fourth ink dots D. In this way, in the four nozzle arrays, partial printing data is divided and assigned to the group of nozzles 1 to 4, the group of nozzles 5 to 8, the group of nozzles 9 to 12, and the group of nozzles 13 to 16. Then, based on the partial printing data assigned to each nozzle group, one of the nozzles in each nozzle group is driven, and an input image is printed using the printing pattern.

[0126] FIG. 20(b) is a diagram illustrating the nozzles used in the fourth nozzle array 304 when printing a fixed print pattern. On the left and right sides of FIG. 20(b), first ink dots A corresponding to the nozzles used in the fourth nozzle array 304 when continuously printing the fifth Level 2 print pattern K25 are shown. As shown in FIG. 20(b), when continuously printing the fifth Level 2 print pattern K25, the first, third, sixth, eighth, ninth, eleventh, fourteenth, and sixteenth nozzles, counting from the end of the fourth nozzle array 304, are used. As such, when printing a fixed print pattern, only half of the 16 nozzles in the fourth nozzle array 304 are used, which indicates a bias in the frequency of nozzle use in the fourth nozzle array 304.

[0127] FIG. 20(c) is a diagram illustrating the nozzles used in the fifth nozzle array 305 when printing a fixed print pattern. On the left and right of FIG. 20(c), second ink dots B corresponding to the nozzles used in the fifth nozzle array 305 when continuously printing the fifth Level 2 print pattern K25 are shown. As shown in FIG. 20(c), when continuously printing the fifth Level 2 print pattern K25, the second, fourth, fifth, seventh, tenth, twelfth, thirteenth, and fifteenth nozzles, counting from the end of the fifth nozzle array 305, are used. As such, when printing a fixed print pattern, only half of the 16 nozzles in the fifth nozzle array 305 are used, which indicates that there is a bias in the frequency of nozzle use in the fifth nozzle array 305.

[0128] FIG. 20(d) is a diagram illustrating the nozzles used in the sixth nozzle array 306 when printing a fixed print pattern. On the left and right sides of FIG. 20(d), third ink dots C are shown corresponding to the nozzles used in the sixth nozzle array 306 when continuously printing the fifth Level 2 print pattern K25. As shown in FIG. 20(d), when continuously printing the fifth Level 2 print pattern K25, the first, third, sixth, eighth, ninth, eleventh, fourteenth, and sixteenth nozzles, counting from the end of the sixth nozzle array 306, are used. Thus, when printing a fixed print pattern, only half of the 16 nozzles in the sixth nozzle array 306 are used, which indicates a bias in the frequency of nozzle use in the sixth nozzle array 306.

[0129] FIG. 20(e) is a diagram illustrating the nozzles used in the seventh nozzle array 307 when printing a fixed print pattern. On the left and right sides of FIG. 20(e), fourth ink dots D corresponding to the nozzles used in the seventh nozzle array 307 when continuously printing the fifth Level 2 print pattern K25 are shown. As shown in FIG. 20(e), when continuously printing the fifth Level 2 print pattern K25, the second, fourth, fifth, seventh, tenth, twelfth, thirteenth, and fifteenth nozzles, counting from the end of the seventh nozzle array 307, are used. Thus, when printing a fixed print pattern, only half of the 16 nozzles in the seventh nozzle array 307 are used, which indicates a bias in the frequency of nozzle use in the seventh nozzle array 307.

[0130] As described in the first embodiment, the ejection elements (electrothermal conversion elements) provided in the nozzles wear out with repeated ejection, and therefore, if there is a bias in the frequency of nozzle use, the life of the print head 101 will be shortened. In step S102 of the third embodiment, the change means 405 of the controller 200 changes the allocation of partial print data for the four nozzle arrays in accordance with the nozzle drive order in each nozzle array, and then proceeds to step S103. At this time, the change means 405 changes the nozzles that are driven based on the partial print data when printing is performed using a fixed print pattern, in accordance with changing the allocation of partial print data in accordance with the nozzle drive order in each nozzle array. This makes it possible to reduce bias in the frequency of nozzle use, even when printing is performed using a fixed print pattern.

[0131] Next, the process of changing the allocation of partial print data in each nozzle array will be described. Fig. 21 is a diagram illustrating the print pattern and nozzle drive order when the allocation of partial print data in each nozzle array has been changed. Fig. 22 is a diagram illustrating the nozzles used in each nozzle array when the allocation of partial print data in each nozzle array has been changed. In the examples shown in Figs. 21 and 22, M=4 and N=16, as in the examples shown in Figs. 19 and 20. Furthermore, the resolution of the input image is 600 dpi, and the drive resolution is 300 dpi.

[0132] FIG. 21(a) is a schematic diagram similar to FIG. 19(a) showing a print pattern for printing an input image at 600 dpi. FIG. 21(b) is a schematic diagram similar to FIG. 19(b) showing the arrangement of dots in a print pattern when printing is performed with a fixed print pattern. FIG. 21(c) is a diagram illustrating the nozzle drive order when the allocation of partial print data in each nozzle array is changed. FIG. 21(c) shows ink dots when ink of the same color is ejected from nozzles in the fourth nozzle array 304, the fifth nozzle array 305, the sixth nozzle array 306, and the seventh nozzle array 307. In the example shown in FIG. 21(c), the numbers 1 to 16 arranged horizontally and the numbers 1 to 16 arranged vertically are the same as the numbers 1 to 16 arranged horizontally and the numbers 1 to 16 arranged vertically in the comparative example shown in FIG. 5. The first ink dot A, the second ink dot B, the third ink dot C, and the fourth ink dot D are similar to the first ink dot A, the second ink dot B, the third ink dot C, and the fourth ink dot D in the example shown in Fig. 19. The first region CM1, the second region CM2, the third region CM3, and the fourth region CM4 are similar to the first region CM1, the second region CM2, the third region CM3, and the fourth region CM4 in the example shown in Fig. 19.

[0133] In the fourth nozzle array 304, the nozzles are driven in the order of the fifth, sixth, ..., sixteenth nozzles counting from the end, followed by the first, second, ..., fourth nozzles, thereby forming a first ink dot A. In the fifth nozzle array 305, the nozzles are driven in the order of the ninth, tenth, ..., sixteenth nozzles counting from the end, followed by the first, second, ..., eighth nozzles, thereby forming a second ink dot B. In the sixth nozzle array 306, the nozzles are driven in the order of the thirteenth, fourteenth, ..., sixteenth nozzles counting from the end, followed by the first, second, ..., twelfth nozzles, thereby forming a third ink dot C. In the seventh nozzle array 307, the nozzles are driven in the order of the first, second, third, fourth, ..., sixteenth nozzles counting from the end, followed by the first, second, ..., twelfth nozzles, thereby forming a fourth ink dot D. 19(c), in the fourth nozzle array 304, the first ink dot A can be formed by driving the nozzles in the order of the first nozzle, the second nozzle, the third nozzle, the fourth nozzle, ..., and the sixteenth nozzle counting from the end. In the fifth nozzle array 305, the second ink dot B can be formed by driving the nozzles in the order of the fifth nozzle, the sixth nozzle, ..., and the sixteenth nozzle counting from the end, and then driving the nozzles in the order of the first nozzle, the second nozzle, ..., and the fourth nozzle. In the sixth nozzle array 306, the third ink dot C can be formed by driving the nozzles in the order of the ninth nozzle, the tenth nozzle, ..., and the sixteenth nozzle counting from the end, and then driving the nozzles in the order of the first nozzle, the second nozzle, ..., and the eighth nozzle. In the seventh nozzle row 307, the fourth ink dot D can be formed by driving the nozzles in the order of the 13th nozzle, the 14th nozzle, ..., the 16th nozzle counting from the end, and then driving the nozzles in the order of the 1st nozzle, the second nozzle, ..., the 12th nozzle.

[0134] The change unit 405 of the controller 200 swaps the drive order of the nozzles in the fourth nozzle array 304 with the drive order of the nozzles in the fifth nozzle array 305. The change unit 405 swaps the drive order of the nozzles in the fifth nozzle array 305 with the drive order of the nozzles in the sixth nozzle array 306. The change unit 405 swaps the drive order of the nozzles in the sixth nozzle array 306 with the drive order of the nozzles in the seventh nozzle array 307. The change unit 405 swaps the drive order of the nozzles in the seventh nozzle array 307 with the drive order of the nozzles in the fourth nozzle array 304. In other words, the change unit 405 changes the allocation of partial print data for each group of the first to fourth nozzles, the fifth to eighth nozzles, the ninth to twelfth nozzles, and the thirteenth to sixteenth nozzles between the fourth to seventh nozzle arrays 304 to 307. In this way, the change means 405 changes the allocation of partial print data in accordance with the nozzle driving order in the fourth to seventh nozzle arrays 304 to 307.

[0135] Figure 22(a) is a diagram illustrating the positional relationship between first ink dots A that can be formed by driving the nozzles of the fourth nozzle array 304 and ink dots when recording is performed with a fixed recording pattern. In the example shown in Figure 22(a), the numbers 1 to 16 lined up vertically are the same as the numbers 1 to 16 lined up vertically in the comparative example shown in Figure 5. The black circles in Figure 22(a) indicate the arrangement of ink dots corresponding to the recording pattern. The shaded areas in Figure 22(a) indicate nozzles in the fourth nozzle array 304 that can form ink dots corresponding to the recording pattern.

[0136] As described above, the change unit 405 changes the allocation of partial print data for each group of nozzles, the first to fourth, the fifth to eighth, the ninth to twelfth, and the thirteenth to sixteenth, between the fourth to seventh nozzle arrays 304 to 307. When the allocation of partial print data for the fourth to seventh nozzle arrays 304 to 307 is changed, as shown in FIG. 22(a), the group of nozzles first to fourth, counting from the end of the fourth nozzle array 304, is driven in the fourth quarter of the drive cycle of the fourth nozzle array 304. Therefore, the group of nozzles first to fourth, counting from the end of the fourth nozzle array 304, forms the first ink dot A, thereby recording pixels on the right side of the fifth Level 2 print pattern K25. The group of nozzles fifth to eighth, counting from the end of the fourth nozzle array 304, is driven in the first quarter of the drive cycle of the fourth nozzle array 304. Therefore, the group of nozzles 5 to 8 counting from the end of the fourth nozzle array 304 forms the first ink dots A, thereby recording pixels on the left side of the fifth Level 2 recording pattern K25. The group of nozzles 9 to 12 counting from the end of the fourth nozzle array 304 is driven in the second quarter of the drive cycle of the fourth nozzle array 304. Therefore, the group of nozzles 9 to 12 counting from the end of the fourth nozzle array 304 forms the first ink dots A, thereby recording pixels on the right side of the fifth Level 2 recording pattern K25. The group of nozzles 13 to 16 counting from the end of the fourth nozzle array 304 is driven in the third quarter of the drive cycle of the fourth nozzle array 304. Therefore, the group of nozzles 13 to 16 counting from the end of the fourth nozzle array 304 forms the first ink dots A, thereby recording pixels on the left side of the fifth Level 2 recording pattern K25.

[0137] Furthermore, the group of nozzles 1 to 4 counting from the end of the fifth nozzle array 305 is driven in the third quarter of the drive cycle of the fifth nozzle array 305. Therefore, the group of nozzles 1 to 4 counting from the end of the fifth nozzle array 305 forms the second ink dots B, thereby recording pixels on the left side of the fifth Lv2 recording pattern K25. The group of nozzles 5 to 8 counting from the end of the fifth nozzle array 305 is driven in the fourth quarter of the drive cycle of the fifth nozzle array 305. Therefore, the group of nozzles 5 to 8 counting from the end of the fifth nozzle array 305 forms the second ink dots B, thereby recording pixels on the right side of the fifth Lv2 recording pattern K25. The group of nozzles 9 to 12 counting from the end of the fifth nozzle array 305 is driven in the first quarter of the drive cycle of the fifth nozzle array 305. Therefore, the group of nozzles 9 to 12 counting from the end of the fifth nozzle array 305 records pixels on the left side of the fifth Level 2 recording pattern K25 by forming the second ink dots B. The group of nozzles 13 to 16 counting from the end of the fifth nozzle array 305 is driven in the second quarter of the drive cycle of the fifth nozzle array 305. Therefore, the group of nozzles 13 to 16 counting from the end of the fifth nozzle array 305 records pixels on the right side of the fifth Level 2 recording pattern K25 by forming the second ink dots B.

[0138] The group of nozzles 1 to 4 counting from the end of the sixth nozzle array 306 is driven in the second quarter of the drive cycle of the sixth nozzle array 306. Therefore, the group of nozzles 1 to 4 counting from the end of the sixth nozzle array 306 forms the third ink dot C, thereby recording pixels on the right side of the fifth Level 2 recording pattern K25. The group of nozzles 5 to 8 counting from the end of the sixth nozzle array 306 is driven in the third quarter of the drive cycle of the sixth nozzle array 306. Therefore, the group of nozzles 5 to 8 counting from the end of the sixth nozzle array 306 forms the third ink dot C, thereby recording pixels on the left side of the fifth Level 2 recording pattern K25. The group of nozzles 9 to 12 counting from the end of the sixth nozzle array 306 is driven in the fourth quarter of the drive cycle of the sixth nozzle array 306. Therefore, the group of nozzles 9 to 12 counting from the end of the fourth nozzle array 304 prints pixels on the right side of the fifth Level 2 recording pattern K25 by forming the third ink dots C. The group of nozzles 13 to 16 counting from the end of the sixth nozzle array 306 is driven in the first quarter of the drive cycle of the sixth nozzle array 306. Therefore, the group of nozzles 13 to 16 counting from the end of the sixth nozzle array 306 prints pixels on the left side of the fifth Level 2 recording pattern K25 by forming the third ink dots C.

[0139] The group of nozzles 1 to 4 counting from the end of the seventh nozzle array 307 is driven in the first quarter of the drive cycle of the seventh nozzle array 307. Therefore, the group of nozzles 1 to 4 counting from the end of the seventh nozzle array 307 forms the fourth ink dot D, thereby recording pixels on the left side of the fifth Lv2 recording pattern K25. The group of nozzles 5 to 8 counting from the end of the seventh nozzle array 307 is driven in the second quarter of the drive cycle of the seventh nozzle array 307. Therefore, the group of nozzles 5 to 8 counting from the end of the seventh nozzle array 307 forms the fourth ink dot D, thereby recording pixels on the right side of the fifth Lv2 recording pattern K25. The group of nozzles 9 to 12 counting from the end of the seventh nozzle array 307 is driven in the third quarter of the drive cycle of the seventh nozzle array 307. Therefore, the group of nozzles 9 to 12 counting from the end of the seventh nozzle array 307 forms the fourth ink dots D, thereby printing pixels on the left side of the fifth Level 2 printing pattern K25. The group of nozzles 13 to 16 counting from the end of the seventh nozzle array 307 is driven in the fourth quarter of the drive cycle of the seventh nozzle array 307. Therefore, the group of nozzles 13 to 16 counting from the end of the seventh nozzle array 307 forms the fourth ink dots D, thereby printing pixels on the right side of the fifth Level 2 printing pattern K25.

[0140] FIG. 22(b) is a diagram illustrating the nozzles used in the fourth nozzle array 304 when the allocation of partial print data in each nozzle array is changed. On the left and right sides of FIG. 22(b), first ink dots A corresponding to the nozzles used in the fourth nozzle array 304 when continuously printing the fifth Level 2 print pattern K25 are shown. As shown in FIG. 22(b), when continuously printing the fifth Level 2 print pattern K25, the second, fourth, fifth, seventh, tenth, twelfth, thirteenth, and fifteenth nozzles, counting from the end of the fourth nozzle array 304, are used. On the other hand, in the example shown in FIG. 20(b), when continuously printing the fifth Level 2 print pattern K25, the first, third, sixth, eighth, ninth, eleventh, fourteenth, and sixteenth nozzles, counting from the end of the fourth nozzle array 304, are used. Comparing the example shown in Figure 22(b) with the example shown in Figure 20(b), it can be seen that the fifth Level 2 recording pattern K25 for recording remains unchanged, but the nozzles used in the fourth nozzle row 304 are changed. By changing the allocation of partial recording data according to the nozzle drive order in the fourth to seventh nozzle rows 304 to 307, the nozzles used in the fourth nozzle row 304 are made uniform, and imbalances in the frequency of nozzle use are reduced.

[0141] FIG. 22(c) is a diagram illustrating the nozzles used in the fifth nozzle array 305 when the allocation of partial print data in each nozzle array is changed. On the left and right sides of FIG. 22(c), second ink dots B corresponding to the nozzles used in the fifth nozzle array 305 when continuously printing the fifth Level 2 print pattern K25 are shown. As shown in FIG. 22(c), when continuously printing the fifth Level 2 print pattern K25, the first, third, sixth, eighth, ninth, eleventh, fourteenth, and sixteenth nozzles, counting from the end of the fifth nozzle array 305, are used. On the other hand, in the example shown in FIG. 20(c), when continuously printing the fifth Level 2 print pattern K25, the second, fourth, fifth, seventh, tenth, twelfth, thirteenth, and fifteenth nozzles, counting from the end of the fifth nozzle array 305, are used. Comparing the example shown in Figure 22(c) with the example shown in Figure 20(c) reveals that the fifth Level 2 recording pattern K25 for recording remains unchanged, but the nozzles used in the fifth nozzle array 305 are changed. By changing the allocation of partial recording data according to the nozzle drive order in the fourth to seventh nozzle arrays 304 to 307, the nozzles used in the fifth nozzle array 305 are made uniform, and imbalances in the frequency of nozzle use are reduced.

[0142] FIG. 22(d) is a diagram illustrating the nozzles used in the sixth nozzle array 306 when the allocation of partial print data in each nozzle array is changed. On the left and right sides of FIG. 22(d), third ink dots C corresponding to the nozzles used in the sixth nozzle array 306 when continuously printing the fifth Level 2 print pattern K25 are shown. As shown in FIG. 22(d), when continuously printing the fifth Level 2 print pattern K25, the second, fourth, fifth, seventh, tenth, twelfth, thirteenth, and fifteenth nozzles, counting from the end of the sixth nozzle array 306, are used. On the other hand, in the example shown in FIG. 20(d), when continuously printing the fifth Level 2 print pattern K25, the first, third, sixth, eighth, ninth, eleventh, fourteenth, and sixteenth nozzles, counting from the end of the sixth nozzle array 306, are used. Comparing the example shown in Figure 22(d) with the example shown in Figure 20(d) reveals that the fifth Level 2 recording pattern K25 for recording remains unchanged, but the nozzles used in the sixth nozzle array 306 are changed. By changing the allocation of partial recording data in accordance with the nozzle drive order in the fourth to seventh nozzle arrays 304 to 307, the nozzles used in the sixth nozzle array 306 are made uniform, and imbalances in the frequency of nozzle use are reduced.

[0143] FIG. 22(e) is a diagram illustrating the nozzles used in the seventh nozzle array 307 when the allocation of partial print data in each nozzle array is changed. On the left and right sides of FIG. 22(e), the fourth ink dots D corresponding to the nozzles used in the seventh nozzle array 307 when continuously printing the fifth Level 2 print pattern K25 are shown. As shown in FIG. 22(e), when continuously printing the fifth Level 2 print pattern K25, the first, third, sixth, eighth, ninth, eleventh, fourteenth, and sixteenth nozzles, counting from the end of the seventh nozzle array 307, are used. Meanwhile, in the example shown in FIG. 20(e), when continuously printing the fifth Level 2 print pattern K25, the second, fourth, fifth, seventh, tenth, twelfth, thirteenth, and fifteenth nozzles, counting from the end of the seventh nozzle array 307, are used. Comparing the example shown in Figure 22(e) with the example shown in Figure 20(e), it can be seen that the fifth Level 2 recording pattern K25 for recording remains unchanged, but the nozzles used in the seventh nozzle row 307 are changed. By changing the allocation of partial recording data according to the nozzle drive order in the fourth to seventh nozzle rows 304 to 307, the nozzles used in the seventh nozzle row 307 are made uniform, and imbalances in the frequency of nozzle use are reduced.

[0144] In the third embodiment, when printing is performed using a fixed print pattern, the change unit 405 changes the allocation of partial print data according to the nozzle drive order in each of the four nozzle arrays. For example, the change unit 405 changes the nozzles driven based on the partial print data to other nozzles in the four nozzle arrays in response to changing the allocation of partial print data according to the nozzle drive order in each of the four nozzle arrays. As a specific example, the change unit 405 changes the allocation of partial print data for each group of nozzles (1st to 4th nozzles, 5th to 8th nozzles, 9th to 12th nozzles, and 13th to 16th nozzles) between the fourth to seventh nozzle arrays 304 to 307. This standardizes the nozzles used in each nozzle array, reducing unevenness in the frequency of nozzle use. Thus, according to the third embodiment, as with the first embodiment, unevenness in the frequency of nozzle use can be reduced when applying pseudo-halftoning to an inkjet printing apparatus.

[0145] As in the first embodiment, the change unit 405 changes the allocation of partial print data according to the nozzle drive order in each of the four nozzle arrays at a predetermined timing for each page to be printed, thereby reducing bias in the nozzle usage frequency while maintaining the printing speed and print quality.

[0146] <<Fourth Embodiment>> Next, a fourth embodiment will be described. Since the individual components in the fourth embodiment have the same configuration as those in the first embodiment, they will be described using the same reference numerals as those in the first embodiment.

[0147] <Method for controlling a recording device> A control method for the recording apparatus 100 according to the fourth embodiment will now be described. In the fourth embodiment, the controller 200 performs the same processing as in the third embodiment, except for the processing of step S102. In other words, the controller 200 performs the same processing as in the first embodiment, except for the processing of step S102, and in that recording is performed using four rows of nozzles (fourth to seventh nozzle rows 304 to 307) that eject ink of the same color. In the fourth embodiment, the pixels in the edge portion are defined as the two outermost pixels among the pixels whose gradation level is Lv1 or higher. In step S102, the change means 405 of the controller 200 changes the recording pattern to be selected from multiple recording patterns when recording is performed using a fixed recording pattern, and the process proceeds to step S103. At this time, the change means 405 changes the nozzles to be driven based on partial recording data when recording is performed using a fixed recording pattern, in response to changing the recording pattern selected by the selection means 401. This makes it possible to reduce bias in the frequency of nozzle use, even when recording is performed using a fixed recording pattern.

[0148] Next, a process for changing the print pattern selected when printing is performed using a fixed print pattern will be described. Fig. 23 is a diagram illustrating the print pattern and the nozzle drive sequence when the print pattern is changed. Fig. 24 is a diagram illustrating the nozzles used in each nozzle array when the print pattern is changed. In the examples shown in Figs. 23 and 24, M=4 and N=16, as in the examples shown in Figs. 19 and 20. Furthermore, the resolution of the input image is 600 dpi, and the drive resolution is 300 dpi.

[0149] FIG. 23(a) is a schematic diagram showing a changed recording pattern. FIG. 23(b) is a schematic diagram showing the dot arrangement of the recording pattern when the recording pattern is changed. The black circles in FIGS. 23(a) and 23(b) indicate the dot arrangement of the changed recording pattern. The change means 405 of the controller 200 changes the recording pattern selected when recording is performed using a fixed recording pattern from the fifth Level 2 recording pattern K25 to the sixth Level 2 recording pattern K26, as shown in FIG. 23(a), for example. In this way, one recording pattern different from the recording pattern selected in step S106 is selected from the prepared Level 2 recording patterns, for example, from the six Level 2 recording patterns mentioned above. Then, as shown in FIG. 23(b), the input image is recorded using the sixth Level 2 recording pattern K26, which is changed from the fifth Level 2 recording pattern K25. FIG. 23(c) is a diagram similar to FIG. 19(c) that explains the nozzle driving sequence when the recording pattern is changed.

[0150] Figure 24(a) is a diagram illustrating the positional relationship between the first ink dots A that can be formed by driving the nozzles of the fourth nozzle row 304 and the ink dots when the recording pattern is changed. In the example shown in Figure 24(a), the numbers 1 to 16 arranged vertically are the same as the numbers 1 to 16 arranged vertically in the comparative example shown in Figure 5. The black circles in Figure 24(a) indicate the arrangement of ink dots corresponding to the recording pattern. The shaded areas in Figure 24(a) indicate the nozzles of the fourth nozzle row 304 that can form ink dots corresponding to the recording pattern.

[0151] As described above, the change unit 405 changes the print pattern selected when printing is performed using a fixed print pattern from the fifth Level 2 print pattern K25 to the sixth Level 2 print pattern K26. The change unit 405 does not change the print data assigned to the fourth to seventh nozzle arrays 304 to 307. Therefore, as shown in FIG. 24(a), the group of nozzles 1 to 4 counting from the end of the fourth nozzle array 304 forms the first ink dots A to print pixels to the left of the sixth Level 2 print pattern K26. The group of nozzles 5 to 8 counting from the end of the fourth nozzle array 304 forms the first ink dots A to print pixels to the right of the sixth Level 2 print pattern K26. The group of nozzles 9 to 12 counting from the end of the fourth nozzle array 304 forms the first ink dots A to print pixels to the left of the sixth Level 2 print pattern K26. The group of nozzles from the 13th to 16th positions counting from the end of the fourth nozzle row 304 forms the first ink dots A, thereby printing the pixels on the right side of the sixth Level 2 printing pattern K26.

[0152] Additionally, the group of nozzles 1 to 4 counting from the end of the fifth nozzle array 305 forms the second ink dots B to record pixels on the right side of the sixth Level 2 recording pattern K26. The group of nozzles 5 to 8 counting from the end of the fifth nozzle array 305 forms the second ink dots B to record pixels on the left side of the sixth Level 2 recording pattern K26. The group of nozzles 9 to 12 counting from the end of the fifth nozzle array 305 forms the second ink dots B to record pixels on the right side of the sixth Level 2 recording pattern K26. The group of nozzles 13 to 16 counting from the end of the fifth nozzle array 305 forms the second ink dots B to record pixels on the left side of the sixth Level 2 recording pattern K26.

[0153] The group of nozzles 1 to 4 counting from the end of the sixth nozzle array 306 records pixels on the left side of the sixth Level 2 recording pattern K26 by forming the third ink dots C. The group of nozzles 5 to 8 counting from the end of the sixth nozzle array 306 records pixels on the right side of the sixth Level 2 recording pattern K26 by forming the third ink dots C. The group of nozzles 9 to 12 counting from the end of the fourth nozzle array 304 records pixels on the left side of the sixth Level 2 recording pattern K26 by forming the third ink dots C. The group of nozzles 13 to 16 counting from the end of the sixth nozzle array 306 records pixels on the right side of the sixth Level 2 recording pattern K26 by forming the third ink dots C.

[0154] The group of nozzles 1 to 4 counting from the end of the seventh nozzle array 307 forms the fourth ink dot D to record pixels on the right side of the sixth Level 2 recording pattern K26. The group of nozzles 5 to 8 counting from the end of the seventh nozzle array 307 forms the fourth ink dot D to record pixels on the left side of the sixth Level 2 recording pattern K26. The group of nozzles 9 to 12 counting from the end of the seventh nozzle array 307 forms the fourth ink dot D to record pixels on the right side of the sixth Level 2 recording pattern K26. The group of nozzles 13 to 16 counting from the end of the seventh nozzle array 307 forms the fourth ink dot D to record pixels on the left side of the sixth Level 2 recording pattern K26.

[0155] FIG. 24(b) is a diagram illustrating the nozzles used in the fourth nozzle array 304 when the recording pattern is changed. On the left and right sides of FIG. 24(b), first ink dots A corresponding to the nozzles used in the fourth nozzle array 304 when continuously recording the sixth Level 2 recording pattern K26 are shown. As shown in FIG. 24(b), when continuously recording the sixth Level 2 recording pattern K26, the second, fourth, fifth, seventh, tenth, twelfth, thirteenth, and fifteenth nozzles, counting from the end of the fourth nozzle array 304, are used. On the other hand, in the example shown in FIG. 20(b), when continuously recording the fifth Level 2 recording pattern K25, the first, third, sixth, eighth, ninth, eleventh, fourteenth, and sixteenth nozzles, counting from the end of the fourth nozzle array 304, are used. Comparing the example shown in Fig. 24(b) with the example shown in Fig. 20(b), it can be seen that there is a change in the nozzles used in the fourth nozzle row 304. By changing the print pattern selected from multiple print patterns when printing is performed using a fixed print pattern, the nozzles used in the fourth nozzle row 304 are made uniform, and bias in the frequency of nozzle use is reduced.

[0156] FIG. 24(c) is a diagram illustrating the nozzles used in the fifth nozzle array 305 when the type of recording pattern is changed. On the left and right sides of FIG. 24(c), second ink dots B corresponding to the nozzles used in the fifth nozzle array 305 when continuously recording the sixth Level 2 recording pattern K26 are shown. As shown in FIG. 24(c), when continuously recording the sixth Level 2 recording pattern K26, the first, third, sixth, eighth, ninth, eleventh, fourteenth, and sixteenth nozzles, counting from the end of the fifth nozzle array 305, are used. On the other hand, in the example shown in FIG. 20(c), when continuously recording the fifth Level 2 recording pattern K25, the second, fourth, fifth, seventh, tenth, twelfth, thirteenth, and fifteenth nozzles, counting from the end of the fifth nozzle array 305, are used. Comparing the example shown in Figure 24(c) with the example shown in Figure 20(c), it can be seen that there is a change in the nozzles used in the fifth nozzle array 305. By changing the print pattern selected from multiple print patterns when printing is performed using a fixed print pattern, the nozzles used in the fifth nozzle array 305 are made uniform, and bias in the frequency of nozzle use is reduced.

[0157] FIG. 24(d) is a diagram illustrating the nozzles used in the sixth nozzle array 306 when the type of recording pattern is changed. On the left and right sides of FIG. 24(d), third ink dots C corresponding to the nozzles used in the sixth nozzle array 306 when continuously recording the sixth Level 2 recording pattern K26 are shown. As shown in FIG. 24(d), when continuously recording the sixth Level 2 recording pattern K26, the second, fourth, fifth, seventh, tenth, twelfth, thirteenth, and fifteenth nozzles, counting from the end of the sixth nozzle array 306, are used. On the other hand, in the example shown in FIG. 20(d), when continuously recording the fifth Level 2 recording pattern K25, the first, third, sixth, eighth, ninth, eleventh, fourteenth, and sixteenth nozzles, counting from the end of the sixth nozzle array 306, are used. Comparing the example shown in Figure 24(d) with the example shown in Figure 20(d), it can be seen that there is a change in the nozzles used in the sixth nozzle row 306. By changing the recording pattern selected from multiple types of recording patterns when recording is performed using a fixed recording pattern, the nozzles used in the sixth nozzle row 306 are made uniform, and bias in the frequency of nozzle use is reduced.

[0158] FIG. 24(e) is a diagram illustrating the nozzles used in the seventh nozzle array 307 when the type of recording pattern is changed. On the left and right sides of FIG. 24(e), the fourth ink dots D corresponding to the nozzles used in the seventh nozzle array 307 when continuously recording the sixth Level 2 recording pattern K26 are shown. As shown in FIG. 24(e), when continuously recording the sixth Level 2 recording pattern K26, the first, third, sixth, eighth, ninth, eleventh, fourteenth, and sixteenth nozzles, counting from the end of the seventh nozzle array 307, are used. On the other hand, in the example shown in FIG. 20(e), when continuously recording the fifth Level 2 recording pattern K25, the second, fourth, fifth, seventh, tenth, twelfth, thirteenth, and fifteenth nozzles, counting from the end of the seventh nozzle array 307, are used. Comparing the example shown in Figure 24(e) with the example shown in Figure 20(e), it can be seen that there is a change in the nozzles used in the seventh nozzle row 307. By changing the recording pattern selected from multiple types of recording patterns when recording is performed using a fixed recording pattern, the nozzles used in the seventh nozzle row 307 are made uniform, and bias in the frequency of nozzle use is reduced.

[0159] In the fourth embodiment, the change unit 405 changes the print pattern selected from among multiple print patterns when printing is performed using a fixed print pattern. Specifically, the change unit 405 changes the nozzles driven based on partial print data to other nozzles in the four nozzle arrays in response to changing the print pattern selected from among multiple print patterns. As a specific example, the change unit 405 changes the print pattern selected when printing is performed using a fixed print pattern from the fifth level 2 print pattern K25 to the sixth level 2 print pattern K26. This standardizes the nozzles used in each nozzle array, reducing unevenness in the frequency of nozzle use. Thus, according to the fourth embodiment, as with the first embodiment, unevenness in the frequency of nozzle use can be reduced when applying pseudo-halftoning to an inkjet printing apparatus.

[0160] As in the first embodiment, the change unit 405 changes the print pattern selected from multiple print patterns when printing is performed using a fixed print pattern at a predetermined timing for each page to be printed. This makes it possible to reduce bias in the frequency of nozzle use while maintaining the print speed and print quality.

[0161] In the above-described embodiments, the predetermined timing for changing the nozzles is set based on the number of pages to be printed (the aforementioned threshold value P1), but this is not limited to this. For example, the predetermined timing may be set based on the number of times the print head 101 moves in the main scanning direction above the printing medium MD. The predetermined timing may also be set based on the movement distance of the print head 101 in the main scanning direction.

[0162] The predetermined timing may also be set based on a certain amount of time that has elapsed. For example, the certain amount of time may be one week from a certain point in time, or a certain amount of time that has elapsed since recording device 100 started recording. The predetermined timing may also be set based on the number of recording commands consisting of multiple pages, also called the number of print jobs.

[0163] As described above, in addition to the first print mode capable of printing edge portions of an input image using a fixed print pattern, a second print mode may be provided in which printing is not performed using a fixed print pattern. The first print mode or the second print mode is set depending on the type of recording medium MD, the print quality specified by the user, and the like. In this case, a predetermined timing may be set in the first print mode. For example, the predetermined timing may be set based on the number of pages printed in the first print mode (the aforementioned threshold value P1). The predetermined timing may be set based on the number of movements of the print head 101 in the first print mode, or based on the movement distance of the print head 101 in the first print mode. The predetermined timing may also be set based on a certain elapsed time in the first print mode.

[0164] In each of the above-described embodiments, the threshold value P1 is set to a fixed value (number of pages), but this is not limited to this. For example, multiple threshold values ​​may be set according to the number of pages. In this case, the threshold value may be set to 10,000 (pages) for up to 60,000 pages after the start of printing, and then set to 5,000 (pages) after 60,000 pages after the start of printing. In cases where the degree of wear of the nozzles (ejection elements) of the print head 101 decreases with increasing number of uses, the predetermined timing for changing the nozzles can be appropriately set.

[0165] Alternatively, the change unit 405 may change the nozzles driven based on the partial print data when it detects a bias in the nozzle usage frequency of the print head 101, instead of at a predetermined timing. In other words, when it detects a bias in the nozzle usage frequency of the print head 101, the change unit 405 may change the allocation of partial print data according to the nozzle drive order in each nozzle row, or the print pattern selected from among multiple print patterns. In this case, the change unit 405 may detect a bias in the nozzle usage frequency of the print head 101 based on the results of counting the number of times ink is ejected from the nozzles of the print head 101. For example, by counting the number of ink dots for each nozzle, it may detect a bias in the nozzle usage frequency of the print head 101 when the number of times ink is ejected from the most frequently used nozzle exceeds a certain number. It may also detect a bias in the nozzle usage frequency of the print head 101 when the average (total) number of times ink is ejected from nozzles that are used relatively frequently exceeds a certain number. Furthermore, the bias in the frequency of nozzle use in the print head 101 may be detected based on the difference between the number of times ink is ejected from the most frequently used nozzle and the number of times ink is ejected from the least frequently used nozzle.

[0166] In each of the above-described embodiments, the recording device 100 records the edge portions of the input image using a fixed recording pattern, but this is not limiting. The recording device 100 may also record portions of the input image other than the edge portions using a fixed recording pattern.

[0167] In the above-described embodiments, the ink ejection method is explained using an example in which a thermal method is used, in which ink is ejected by generating bubbles using an electrothermal conversion element, but the present invention is not limited to this. For example, a method in which ink is ejected using a piezoelectric element (piezo) may also be used.

[0168] In the above-described embodiments, examples where recording is performed using a Level 2 recording pattern have been mainly described, but the present invention is not limited to this. For example, recording may be performed using a Level 3 recording pattern or a Level 1 recording pattern.

[0169] In the above-described embodiments, the number of drivable nozzles in each nozzle row is the same as the number of nozzles arranged in each nozzle row, but this is not limited to this. For example, the number of drivable nozzles in each nozzle row may be smaller than the number of nozzles arranged in each nozzle row. Specifically, the number of nozzles arranged in each nozzle row may be 20, while the number of drivable nozzles in each nozzle row may be 16. In this case, of the 20 nozzles arranged in each nozzle row, typically, two nozzles at each end are not driven, and 16 nozzles in the center are driven. When misalignment of the print head 101 (16 nozzles) in the Y direction is detected, at least one of the two nozzles at each end is driven to correct the misalignment of the 16 nozzles. The two nozzles at each end of the 20 nozzles are also referred to as registration nozzles.

[0170] In each of the above-described embodiments, the print head 101 is a so-called serial print head that ejects ink while moving in the main scanning direction, but is not limited to this. The print head may also be a so-called full-line print head that is capable of ejecting ink across the entire width of the print medium MD without moving in the main scanning direction.

[0171] <<Other embodiments>> The disclosure of the present embodiment includes configurations typified by the following recording device example, recording device control method example, and program example.

[0172] <Configuration 1> An inkjet recording apparatus equipped with a recording head having M rows of nozzles (M is a natural number of 2 or more) capable of ejecting ink of the same color, a selection means for determining a gradation level for each pixel in an input image by performing pseudo-halftoning on the input image, and selecting a recording pattern corresponding to the gradation level for each pixel from a plurality of types of recording patterns prepared in advance; a setting means for setting a drive order of N nozzles (N is a multiple of M) that can be driven in each of the M nozzle rows by shifting the drive cycle between the M nozzle rows by N / M nozzles; a dividing means for dividing print data including a nozzle drive sequence for performing printing at a resolution higher than the drive resolution of each nozzle of each nozzle array using the print pattern into M groups obtained by shifting the drive sequence of the N nozzles by N / M nozzles; an allocation means for distributing and allocating partial print data obtained by dividing the partial print data into the M groups to the M nozzle arrays in accordance with the nozzle driving order in each of the nozzle arrays; a change unit that, when performing the printing using the fixed printing pattern, changes the allocation of the partial printing data in accordance with the nozzle driving sequence in each nozzle array, or changes the selected printing pattern; A recording device comprising:

[0173] <Configuration 2> The recording device according to configuration 1, wherein the change means changes the nozzles driven based on the partial recording data to other nozzles in the M nozzle rows in response to changing the allocation of the partial recording data according to the driving order of the nozzles in each of the nozzle rows.

[0174] <Configuration 3> 2. The recording apparatus according to configuration 1, wherein the change unit changes the nozzles driven based on the partial recording data to other nozzles in the M nozzle rows in response to a change in the selected recording pattern.

[0175] <Configuration 4> 4. The recording device according to any one of configurations 1 to 3, wherein the change unit changes the allocation of the partial recording data in accordance with the driving order of the nozzles in each of the nozzle arrays, or the selected recording pattern, at a predetermined timing.

[0176] <Configuration 5> 5. The recording device according to configuration 4, wherein the predetermined timing is set based on the number of pages on which the recording is to be performed.

[0177] <Configuration 6> 5. The recording apparatus according to configuration 4, wherein the predetermined timing is set based on the number of times or the distance of movement of the recording head.

[0178] <Configuration 7> 5. The recording device according to configuration 4, wherein the predetermined timing is set based on a certain elapsed time.

[0179] <Configuration 8> 8. The recording apparatus according to any one of configurations 5 to 7, wherein the predetermined timing is set in a recording mode in which the recording can be performed using a fixed recording pattern.

[0180] <Configuration 9> The recording device according to any one of configurations 1 to 3, wherein the change unit, when detecting a bias in the frequency of nozzle use in the recording head, changes the allocation of the partial recording data according to the nozzle drive order in each nozzle row, or the selected recording pattern.

[0181] <Configuration 10> 10. The recording apparatus according to claim 9, wherein the change unit detects a bias in the frequency of use of the nozzles in the recording head based on a result of counting the number of times ink is ejected from the nozzles of the recording head.

[0182] <Configuration 11> 11. The recording device according to any one of configurations 1 to 10, wherein the recording pattern is fixed and used to record an edge portion of the input image.

[0183] <Configuration 12> 12. The recording device according to configuration 11, wherein the recording pattern is switched for each pixel of the input image to record a non-edge portion of the input image excluding the edge portion.

[0184] <Configuration 13> A control method for an inkjet recording device equipped with a recording head having M rows of nozzles (M is a natural number of 2 or more) capable of ejecting ink of the same color, comprising: a step of performing pseudo-halftoning on an input image to obtain a gradation level for each pixel in the input image, and selecting a recording pattern corresponding to the gradation level for each pixel from a plurality of types of recording patterns prepared in advance; setting a drive order for N (N is a multiple of M) nozzles that can be driven in each of the M nozzle rows by shifting the drive cycle by N / M nozzles between the M nozzle rows; dividing print data including a nozzle drive sequence for performing printing at a resolution higher than the drive resolution of each nozzle in each of the nozzle arrays using the print pattern into M groups obtained by shifting the drive sequence of the N nozzles by N / M nozzles; a step of distributing and allocating partial print data obtained by dividing the partial print data into the M groups to the M nozzle arrays in accordance with the nozzle driving order in each of the nozzle arrays; when performing the printing using the fixed printing pattern, changing the allocation of the partial printing data in accordance with the nozzle driving order in each nozzle array, or changing the selected printing pattern; 10. A method for controlling a recording apparatus, comprising:

[0185] <Configuration 14> 14. A program for causing a computer to execute the recording device control method according to claim 13. [Explanation of symbols]

[0186] 100 Recording device 101 Recording head 130 Ink ejection section 200 Controller 301 First nozzle row 302 Second nozzle row 303 3rd nozzle row 304 4th nozzle row 305 5th nozzle row 306 6th nozzle row 307 7th nozzle row 308 8th nozzle row 309 9th nozzle row 310 10th nozzle row

Claims

1. An inkjet recording apparatus equipped with a recording head having M rows of nozzles (M is a natural number of 2 or more) capable of ejecting ink of the same color, a selection means for determining a gradation level for each pixel in an input image by performing pseudo-halftoning on the input image, and selecting a recording pattern corresponding to the gradation level for each pixel from a plurality of types of recording patterns prepared in advance; a setting means for setting a drive order of N nozzles (N is a multiple of M) that can be driven in each of the M nozzle arrays by shifting the drive cycle between the M nozzle arrays by N / M nozzles; a dividing means for dividing print data including a nozzle drive sequence for performing printing at a resolution higher than the drive resolution of each nozzle of each nozzle array using the print pattern into M groups obtained by shifting the drive sequence of the N nozzles by N / M nozzles; an allocation means for distributing and allocating partial print data obtained by dividing the partial print data into the M groups to the M nozzle arrays in accordance with the nozzle driving order in each of the nozzle arrays; a change unit that, when performing the printing using the fixed printing pattern, changes the allocation of the partial printing data in accordance with the nozzle driving sequence in each nozzle array, or changes the selected printing pattern; A recording device comprising:

2. 2. The printing apparatus according to claim 1, wherein the change means changes the nozzles driven based on the partial printing data to other nozzles in the M nozzle rows in accordance with changing the allocation of the partial printing data according to the driving order of the nozzles in each nozzle row.

3. 2. The printing apparatus according to claim 1, wherein said change means changes the nozzles driven based on said partial print data to other nozzles in said M nozzle rows in response to a change in said selected print pattern.

4. 2. The printing apparatus according to claim 1, wherein the change unit changes the allocation of the partial print data in accordance with the nozzle drive order in each of the nozzle arrays, or the selected print pattern, at a predetermined timing.

5. 5. The recording apparatus according to claim 4, wherein the predetermined timing is set based on the number of pages on which the recording is to be performed.

6. 5. The recording apparatus according to claim 4, wherein the predetermined timing is set based on the number of times or the distance of movement of the recording head.

7. 5. The recording apparatus according to claim 4, wherein the predetermined timing is set based on a certain elapsed time.

8. 8. The recording apparatus according to claim 5, wherein the predetermined timing is set in a recording mode in which the recording can be performed using the fixed recording pattern.

9. 2. The printing apparatus according to claim 1, wherein the change means, when detecting a bias in the frequency of nozzle use in the print head, changes the allocation of the partial print data according to the nozzle drive order in each nozzle row, or the selected print pattern.

10. 10. The recording apparatus according to claim 9, wherein said changing means detects a bias in the frequency of use of the nozzles in said recording head based on a result of counting the number of times ink is ejected from the nozzles of said recording head.

11. 2. The recording apparatus according to claim 1, wherein the edge portion of the input image is recorded using the fixed recording pattern.

12. 12. The recording apparatus according to claim 11, wherein the recording pattern is switched for each pixel of the input image to record a non-edge portion of the input image excluding the edge portion.

13. A control method for an ink jet recording device equipped with a recording head having M (M is a natural number of 2 or more) nozzle arrays capable of ejecting ink of the same color, comprising: a step of performing pseudo-halftoning on an input image to obtain a gradation level for each pixel in the input image, and selecting a recording pattern corresponding to the gradation level for each pixel from a plurality of types of recording patterns prepared in advance; setting a drive order for N nozzles (N is a multiple of M) that can be driven in each of the M nozzle arrays by shifting the drive cycles of the nozzles by N / M nozzles among the M nozzle arrays; dividing print data including a nozzle drive sequence for performing printing at a resolution higher than the drive resolution of each nozzle in each of the nozzle arrays using the print pattern into M groups obtained by shifting the drive sequence of the N nozzles by N / M nozzles; a step of distributing and allocating partial print data obtained by dividing the partial print data into the M groups to the M nozzle arrays in accordance with the nozzle driving order in each of the nozzle arrays; changing the allocation of the partial print data or the selected print pattern in accordance with the nozzle drive order in each nozzle array when performing the printing using the fixed print pattern; 10. A method for controlling a recording apparatus, comprising:

14. A program for causing a computer to execute the recording apparatus control method according to claim 13.

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