Method for adjusting the droplet ejection head in a printing system and printing system

Abstract

The procedure for adjusting the position of the head to be adjusted is simplified, while also taking into account the positions of adjacent heads to be adjusted to ensure proper positioning of the head to be adjusted. [Solution] The adjustment method includes forming a first pattern and a second pattern on a single medium using the adjustment target head; forming the first pattern and the second pattern on the single medium using a reference head adjacent to the adjustment target head; calculating the angle of the adjustment target head with respect to a first direction from the first pattern formed on the medium by the adjustment target head; correcting the position of the adjustment target head in the first and second directions based on the calculated angle; and calculating the distance in the first direction and the distance in the second direction between the second pattern formed by the reference head and the corrected second pattern formed by the adjustment target head.

Description

Technical Field

[0001] The present invention relates to a method for adjusting a droplet ejection head in a printing system and a printing system.

Background Art

[0002] Conventionally, there is a line printer that prints an image on a sheet by ejecting ink droplets from a head unit onto the sheet conveyed in the conveyance direction. In such a line printer, the head unit has a plurality of heads arranged in the sheet width direction orthogonal to the conveyance direction. For example, Patent Document 1 discloses an adjustment method capable of easily adjusting the position of each head in the head unit. In this adjustment method, the inclination of the head and the position of the head in the sheet width direction are adjusted by printing a pattern for adjusting the position of the head once.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above adjustment method, when adjusting the position of a head in the sheet width direction, the position of the head adjacent to the head in the sheet width direction is not considered.

[0005] Here, generally, the head unit has a plurality of head support portions for supporting a plurality of heads, and the plurality of head support portions each have dimensional tolerances. Also, each of the plurality of heads has dimensional tolerances. Therefore, even if the position of one head in the sheet width direction is adjusted, unless the position of the head adjacent to the head in the sheet width direction is considered, the interval between the nozzle row of the head and the nozzle row of the head adjacent to the head may deviate.

[0006] The present invention was made to solve the above-mentioned problems, and aims to provide a method for adjusting a droplet ejection head in a printing system and a printing system that can adjust the position of the head to be adjusted while simplifying the procedure for adjusting the position of the head to be adjusted, and taking into account the position of heads adjacent to the head to be adjusted.

[0007] According to an aspect of the present invention, a method for adjusting droplet ejection heads, performed by a controller in a printing system, is provided. The printing system comprises a line head including a plurality of droplet ejection heads, each of the plurality of droplet ejection heads having an ejection surface extending in a first direction and a second direction perpendicular to the first direction, and the plurality of droplet ejection heads being aligned along the first direction; a first actuator for rotating each of the plurality of droplet ejection heads within the line head with respect to the first direction along a virtual plane including the ejection surface; a second actuator for moving each of the plurality of droplet ejection heads within the line head along the first direction; and a scanner.The adjustment method involves: discharging droplets from a head to be adjusted, included in the line head, onto a medium being transported in the second direction, thereby forming a first pattern on the medium indicating the angle of the head to be adjusted relative to the first direction on the virtual plane, and a second pattern indicating the position of the head to be adjusted in the first and second directions; discharging droplets from a reference head adjacent to the head to be adjusted, included in the line head, onto a medium being transported in the second direction, thereby forming a first pattern on the medium indicating the angle of the reference head relative to the first direction on the virtual plane, and a second pattern indicating the position of the reference head in the first and second directions; and having the scanner read the first and second patterns formed by the head to be adjusted and the first and second patterns formed by the reference head. The method includes: calculating the angle of the adjustment target head from the first pattern read by the scanner; correcting the position of the second pattern by the adjustment target head in the first and second directions based on the calculated angle; calculating a first distance in the first direction and a second distance in the second direction between the second pattern by the reference head and the corrected second pattern by the adjustment target head; causing the first actuator to rotate the adjustment target head by the calculated angle; causing the second actuator to move the adjustment target head along the first direction without moving the reference head according to the first distance; and adjusting the discharge timing from the adjustment target head without changing the discharge timing from the reference head according to the second distance.

[0008] According to another aspect of the present invention, a printing system is provided comprising: a line head including a plurality of droplet ejection heads, each of the plurality of droplet ejection heads having an ejection surface extending in a first direction and a second direction perpendicular to the first direction, and the plurality of droplet ejection heads being aligned along the first direction; a first actuator for rotating each of the plurality of droplet ejection heads within the line head with respect to the first direction along a virtual plane including the ejection surface; a second actuator for moving each of the plurality of droplet ejection heads within the line head along the first direction; a scanner; and an electrically connected controller to the line head, the first actuator, the second actuator, and the scanner.The controller discharges droplets onto a medium being transported in the second direction from the head to be adjusted, which is included in the line head, to form a first pattern on the medium indicating the angle of the head to be adjusted with respect to the first direction on the virtual plane, and a second pattern indicating the position of the head to be adjusted in the first and second directions. The controller also discharges droplets onto the medium being transported in the second direction from a reference head adjacent to the head to be adjusted, which is included in the line head, to form a first pattern on the medium indicating the angle of the reference head with respect to the first direction on the virtual plane, and a second pattern indicating the position of the reference head in the first and second directions. The first and second patterns formed by the head to be adjusted and the first and second patterns formed by the reference head are then skimmed together. The scanner reads the first pattern of the head to be adjusted, the angle of the head to be adjusted is calculated from the first pattern read by the scanner, the position of the second pattern of the head to be adjusted in the first and second directions is corrected based on the calculated angle, a first distance is calculated, which is the distance in the first direction, and a second distance is calculated, which is the distance in the second direction, between the second pattern of the reference head and the corrected second pattern of the head to be adjusted, the first actuator rotates the head to be adjusted by the calculated angle, the second actuator moves the head to be adjusted along the first direction without moving the reference head according to the first distance, and the discharge timing from the head to be adjusted is adjusted according to the second distance without changing the discharge timing from the reference head.

[0009] According to the above embodiment of the present invention, the procedure for adjusting the position of the head to be adjusted can be simplified, while the position of the head to be adjusted can be appropriately adjusted by taking into account the position of the head adjacent to the head to be adjusted. [Brief explanation of the drawing]

[0010] [Figure 1]This is a plan view illustrating the configuration of the printing system. [Figure 2] This is a bottom view showing an example of the printing unit that makes up a printing system. [Figure 3] This is a plan view showing an example of a line head that makes up a printer. [Figure 4] This is a cross-sectional view of the flow path member and actuator member that constitute the head. [Figure 5] This flowchart shows how to adjust the print head in a printing system. [Figure 6] This figure shows an example of a test pattern. [Figure 7] Figures 7(a) to 7(c) illustrate the method for calculating the angle relative to the width direction of the head to be adjusted. [Figure 8] This diagram illustrates how to calculate the distance in the transport direction between the test pattern to be adjusted and the reference test pattern. [Figure 9] This figure shows an example of how to adjust the head. [Figure 10] This figure shows an example of how to adjust the head. [Modes for carrying out the invention]

[0011] As shown in Figure 1, the printing system 1000 according to an embodiment of the present invention comprises a printer 100, a PC 200, and a scanner 300. The printer 100 is a digital printing machine.

[0012] As an example, the PC200 includes a CPU210, memory220 such as RAM, a storage unit230 such as a hard disk drive, an input unit240 such as a keyboard, a display unit250 such as a display, and an input / output interface260 such as USB. The CPU210 temporarily reads data and programs stored in the storage unit230 into the memory220 and executes various processes described later according to the read data and programs. The printer100 and scanner300 are electrically connected to the PC200 via the input / output interface260.

[0013] Next, the configuration of the printer 100 will be described in detail. As shown in Figure 2, the printer 100 mainly consists of line heads 10A to 10H, a transport device 20, and head controllers 6A to 6H.

[0014] The line heads 10A to 10H are arranged in this order from the upstream side in the transport direction. The transport direction is the direction in which the medium M, such as roll paper, is transported by the transport device 20. Each of the line heads 10A to 10H is long in the width direction. The width direction is along the width of the medium M and is perpendicular to the vertical direction and the transport direction. Each of the line heads 10A to 10H ejects ink onto the medium M while fixed in position on the housing (not shown) of the printer 100. The width direction is an example of the first direction of the present invention, and the transport direction is an example of the second direction of the present invention.

[0015] Line heads 10C to 10H on the downstream side in the conveying direction are supplied with, for example, yellow, orange, magenta, violet, cyan, and black inks, respectively. Line heads 10A and 10B on the upstream side in the conveying direction are supplied with, for example, white ink, respectively. As these inks, for example, UV-curable inks that harden when exposed to ultraviolet (UV) light can be used.

[0016] As shown in Figure 3, each of the line heads 10A to 10H has a frame FR, and at its vertically lower end, there are, for example, 10 droplet discharge heads 1 (hereinafter simply referred to as "head 1"). The 10 heads 1 are arranged in a staggered pattern in the width direction, with their lower surfaces lying on the same plane. The lower surface of each head 1 is a nozzle surface NS from which multiple nozzles N open, as shown in Figure 3. On the nozzle surface NS, the multiple nozzles N are arranged in a staggered pattern in the width direction, forming two rows of nozzles aligned in the transport direction. Each row of nozzles extends in the width direction. In this embodiment, each head 1 has two rows of nozzles, but there may be one row of nozzles, or three or more rows. The nozzle surface NS is an example of a discharge surface of the present invention.

[0017] In addition, each head 1 is provided with a first actuator 5A and a second actuator 5B, such as an eccentric pin, for example. Both the first actuator 5A and the second actuator 5B are configured to be displaced by the drive of a motor fixed to each frame FR of the line heads 10A to 10H, for example. The first actuator 5A adjusts the angle of the head 1 with respect to the width direction by rotating the head 1 along a virtual plane including the nozzle surface NS with respect to the width direction. The second actuator 5B adjusts the position of the head 1 in the width direction by moving the head 1 along the width direction. And, a driver IC4 (see FIG. 4) for applying a drive voltage to the head 1 is electrically connected to each head 1.

[0018] The conveying device 20 includes a feeding roller 20A and a collecting roller 20B shown in FIG. 2, and a plurality of conveying rollers (not shown). Further, the conveying device 20 includes a conveying motor (not shown) connected to the feeding roller 20A and the collecting roller 20B. The feeding roller 20A and the collecting roller 20B are arranged in the conveying direction, and the feeding roller 20A is located upstream in the conveying direction with respect to the collecting roller 20B. In the conveying direction, the line heads 10A to 10H are located between the feeding roller 20A and the collecting roller 20B. The plurality of conveying rollers are located between the feeding roller 20A and the collecting roller 20B in the conveying direction and are arranged in the conveying direction. The plurality of conveying rollers are located below the line heads 10A to 10H.

[0019] The supply roller 20A, the recovery roller 20B, and the plurality of conveyance rollers all extend in the width direction and rotate about a rotation axis extending in the width direction. The supply roller 20A and the recovery roller 20B are each rotationally driven by a conveyance motor. A roll-shaped medium M having a length in the conveyance direction longer than the length in the width direction is attached to the supply roller 20A. The medium M sent out from the supply roller 20A by the rotation of the supply roller 20A passes between the line heads 10A to 10H and the plurality of conveyance rollers and is wound around the recovery roller 20B by the rotation of the recovery roller 20B. Thereby, the medium M is conveyed in the conveyance direction. The plurality of conveyance rollers rotate as the medium M is conveyed. The conveyance motor rotationally drives the supply roller 20A and the recovery roller 20B so that the medium M is conveyed while contacting the upper portions of the circumferential surfaces of the plurality of conveyance rollers respectively.

[0020] The head controllers 6A to 6H are each electrically connected to the line heads 10A to 10H. For example, the head controller 6A is electrically connected to the ten driver ICs 4 included in the line head 10A. Further, the head controller 6A is also electrically connected to the ten first motors and the ten second motors fixed to the frame FR of the line head 10A. The head controllers 6A to 6H all include a processor 61 such as a CPU, a ROM 62, and a RAM 63. When the CPU 61 receives various instructions from the PC 200 shown in FIG. 1, it temporarily reads out the data and programs stored in the ROM 62 into the RAM 63 and executes processing according to the various instructions in accordance with the read data and programs. And the head controllers 6A to 6H are each electrically connected to the PC 200. The CPU 210 of the PC 200 and / or the CPU 61 of each of the head controllers 6A to 6H functions as an example of the controller of the present invention.

[0021] Next, the configuration of each head 1 will be described. As shown in FIG. 4, the head 1 includes a flow path member 2 and a piezoelectric actuator 3.

[0022] The flow path member 2 is formed from a plurality of metal plates and a nozzle plate NP stacked in the vertical direction. Ink flow paths, such as individual flow paths 2B including pressure chambers P and a supply manifold 2A, are formed on the plurality of metal plates by etching. The nozzle plate NP is formed from a polymer synthetic resin material such as polyimide and is bonded to the lower surface of the stacked metal plates with an adhesive. The lower surface of the nozzle plate NP is the nozzle surface NS, which serves as the ink discharge surface through which the nozzle N opens. The nozzle plate NP may also be formed from a metal material such as stainless steel.

[0023] Inside the flow channel member 2, individual flow channels 2B communicating with each nozzle N and a supply manifold 2A communicating with the individual flow channels 2B are formed. Although not shown, the supply manifold 2A extends in the width direction (perpendicular to the plane of the paper in Figure 4). The supply manifold 2A is connected to a tank (not shown) located outside the head 1 via an ink supply port (not shown) formed in the flow channel member 2. Ink coming out of the tank flows into the supply manifold 2A via the ink supply port and is supplied from the supply manifold 2A to the individual flow channels 2B.

[0024] Although not shown in the diagram, the flow channel member 2 has multiple individual flow channels 2B, each corresponding to one of the multiple nozzles N. As described above, the multiple nozzles N each form two rows of nozzles extending in the width direction, and similarly, the multiple individual flow channels 2B each form two rows of individual flow channels extending in the width direction. The supply manifold 2A communicates with the multiple individual flow channels 2B that constitute the two rows of individual flow channels. The number of supply manifolds 2A formed in the flow channel member 2 is adjusted to match the number of nozzles N. Furthermore, when multiple supply manifolds 2A are formed, the number of individual flow channels 2B communicating with each supply manifold 2A is also adjusted to match the number of nozzles N.

[0025] As shown in Figure 4, the piezoelectric actuator 3 is fixed to the upper surface of the flow channel member 2. The piezoelectric actuator 3 includes a metal diaphragm 3A, a piezoelectric layer 3B, and a plurality of individual electrodes 3C.

[0026] The piezoelectric actuator 3 is formed by sequentially depositing a thin film that will become the piezoelectric layer 3B and a thin film that will become the individual electrodes 3C on the upper surface of the diaphragm 3A.

[0027] The diaphragm 3A is positioned on the upper surface of the flow channel member 2 so as to cover all of the pressure chambers P. The diaphragm 3A is a metal plate that is approximately rectangular in shape when viewed from above. The upper surface of the conductive diaphragm 3A is located below the piezoelectric layer 3B. Therefore, the upper surface of the diaphragm 3A can also serve as a common electrode. As a common electrode, the diaphragm 3A is connected to the ground wiring of the driver IC 4 that drives the actuator member 3 and is always maintained at ground potential. Note that the diaphragm 3A does not necessarily have to be a metal plate; for example, it may be formed from the same piezoelectric material as the piezoelectric layer 3B, with a metal film formed on its upper surface to serve as a common electrode.

[0028] The piezoelectric layer 3B is located on the upper surface of the diaphragm 3A. The piezoelectric layer 3B is formed from a piezoelectric material whose main component is lead zirconate titanate (PZT), a ferroelectric solid solution of lead titanate and lead zirconate. The piezoelectric layer 3B is polarized vertically at least in the region facing the pressure chamber P (the portion sandwiched between the individual electrodes 3C and the diaphragm 3A).

[0029] The individual electrodes 3C are arranged on the upper surface of the piezoelectric layer 3B so as to overlap the pressure chamber P vertically. The diaphragm 3A, which acts as a common electrode, the individual electrodes 3C, and the portion of the piezoelectric layer 3B sandwiched between the individual electrodes 3C and the diaphragm 3A form a single piezoelectric element 3X.

[0030] When a predetermined drive voltage is applied to an individual electrode 3C from the driver IC 4, a potential difference is created between the individual electrode 3C to which this drive voltage is applied and the diaphragm 3A, which is a common electrode held at ground potential. As a result, an electric field acts in the thickness direction on the piezoelectric layer 3B sandwiched between the individual electrode 3C and the diaphragm 3A. The direction of this electric field is parallel to the polarization direction of the piezoelectric layer 3B. Therefore, the region of the piezoelectric layer 3B facing the individual electrode 3C (active region) contracts in a planar direction perpendicular to the thickness direction. Here, the diaphragm 3A below the piezoelectric layer 3B is fixed to the flow channel member 2. Therefore, as the piezoelectric layer 3B located on the upper surface of the diaphragm 3A contracts in the planar direction, the portion of the diaphragm 3A covering the pressure chamber P deforms so that it becomes convex toward the pressure chamber P (unimorph deformation). At this time, the volume inside the pressure chamber P decreases, the ink pressure inside the pressure chamber P increases, and ink is ejected from the nozzle N that communicates with this pressure chamber P. In other words, the piezoelectric actuator 3 is located in a position corresponding to the pressure chamber P and applies pressure to the ink in the pressure chamber P in order to eject ink from the nozzle N.

[0031] Next, the adjustment method for the head 1 in the printing system 1000 of this embodiment will be explained with reference to Figures 5 to 10. This adjustment method is performed, for example, when a user replaces any of the heads 1 in any of the line heads 10A to 10H, in order to adjust the angle in the width direction, position in the width direction, ejection timing, and drive voltage of the replaced head 1. If the angle of the replaced head 1 with respect to the transport direction is θ, then the angle of the replaced head 1 with respect to the width direction can be expressed as ((π / 2)-θ). Therefore, calculating the angle of the replaced head 1 with respect to the width direction is equivalent to calculating the angle of the replaced head 1 with respect to the transport direction.

[0032] The flow shown in Figure 5 is initiated when the user specifies the replaced head 1 as the head to be adjusted and inputs a test pattern print command via the input unit 240 of the PC200. The following explanation will use the case where head 1 included in line head 10H is replaced as an example, but the flow is the same when head 1 included in the other line heads 10A to 10G is replaced.

[0033] When the CPU 210 of the PC200 receives a test pattern print instruction via the input unit 240, it sends the instruction to the head controller 6H. Upon receiving the test pattern print instruction, the head controller 6H drives all 10 heads 1 included in the line head 10H to eject ink droplets, thereby printing 10 identical test patterns TP arranged in the width direction onto the medium M being transported in the transport direction (step S10).

[0034] Here, each test pattern TP consists of a first pattern P1, a second pattern P2, and a third pattern P3, as shown in Figure 6. The first pattern P1 is used to calculate the angle of head 1 with respect to the width direction on a virtual plane including the nozzle surface NS. The second pattern P2 is a pattern that shows the positional relationship in the width direction and transport direction between the head to be adjusted and the reference head 1, which is a head 1 adjacent to the head to be adjusted in the width direction. The third pattern P3 is used to measure the print density of the head to be adjusted. As mentioned above, calculating the angle of head 1 with respect to the width direction on a virtual plane including the nozzle surface NS is equivalent to calculating the angle of head 1 with respect to the transport direction on a virtual plane including the nozzle surface NS.

[0035] The first pattern P1 consists of multiple lines (hereinafter referred to as vertical lines) that extend in the transport direction. Each vertical line is formed by continuously ejecting ink droplets from a single nozzle N. In the first pattern P1, the multiple vertical lines are arranged in the width direction.

[0036] The second pattern P2 consists of a vertical pattern P21 and a horizontal pattern P22. The vertical pattern P21 consists of a two-dimensional code and multiple vertical lines. The two-dimensional code contains identification information of the head 1 that printed the test pattern TP containing the two-dimensional code. In the vertical pattern P21, the multiple vertical lines are formed on both sides in the width direction and on the upstream side in the transport direction relative to the two-dimensional code. The horizontal pattern P22 consists of multiple lines (hereinafter referred to as horizontal lines) each extending in the width direction. Each horizontal line is formed by ejecting an ink droplet only once from all nozzles N. In the horizontal pattern P22, the multiple horizontal lines are aligned in the transport direction.

[0037] The third pattern P3 consists of two rectangular solid color patterns of different densities. The third pattern P3 is formed by continuously ejecting ink droplets from all nozzles N.

[0038] When printing the test pattern TP while transporting the medium M in the transport direction, the third pattern P3 is printed first, followed by the first pattern P1, the vertical pattern P21, and the horizontal pattern P22. Here, assuming that the prints are in the order of first pattern P1, third pattern P3, vertical pattern P21, and horizontal pattern P22, when ink droplets are ejected from all nozzles N during the printing of the third pattern P3, a phenomenon occurs where the print density differs between the nozzles N used for printing the first pattern P1 and those that were not used. For this reason, in this embodiment, the third pattern P3 is printed first, and after ink droplets have been ejected from all nozzles N, the first pattern P1, the vertical pattern P21, and the horizontal pattern P22 are printed.

[0039] Returning to the flowchart in Figure 5, when the user inputs a reading instruction for the test pattern TP printed on the medium M via the input unit 240 of the PC200, the CPU 210 of the PC200 drives all 10 heads 1 to cause the scanner 300 to read the 10 test pattern TP printed on the medium M (step S20).

[0040] Next, the CPU 210 of PC200 acquires and analyzes the image data of the 10 test patterns TP read by the scanner 300 (step S30).

[0041] Specifically, the CPU 210 of the PC200 identifies, from among the 10 test pattern TPs, the test pattern TP printed by head 1 designated as the head to be adjusted (hereinafter referred to as the "test pattern TP to be adjusted") and the test pattern TP printed by head 1 adjacent to the head to be adjusted (hereinafter referred to as the "reference head 1") (hereinafter referred to as the "reference test pattern TP"), using the two-dimensional code contained in each test pattern TP.

[0042] For example, if head 1 located at the far left in Figure 3 is designated as the head to be adjusted, then the single head 1 located second from the left in Figure 3 becomes the reference head 1. If head 1 located second from the left in Figure 3 is designated as the head to be adjusted, then the two heads 1 located at the far left and third from the left in Figure 3 become the reference head 1.

[0043] The CPU 210 of the PC200 then calculates the angle of the head to be adjusted relative to the width direction on a virtual surface including the nozzle surface NS, and the distance in the width direction and the distance in the transport direction between the corrected test pattern TP to be adjusted and the reference test pattern TP. Furthermore, the CPU 210 of the PC200 calculates the difference in print density between the test pattern TP to be adjusted and the reference test pattern TP. Details of these calculation methods will be described later.

[0044] Returning to the flowchart in Figure 5, the CPU 210 of PC200 displays the analysis results from step S30 on the display unit 250 of PC200 (step S40).

[0045] The user checks the analysis results displayed on the PC200's display unit 250 and inputs whether adjustment is necessary for the angle relative to the width direction, the position in the width direction, the position in the transport direction, and the density of the test pattern TP to be adjusted, via the PC200's input unit 240.

[0046] If the CPU 210 of PC200 receives input indicating that angle adjustment in the width direction is necessary (step S50: YES), the CPU 210 of PC200 adjusts the angle of the head to be adjusted in the width direction (step S60). Specifically, the CPU 210 of PC200 sends an angle adjustment instruction for the head to be adjusted to the head controller 6H. Upon receiving the angle adjustment instruction for the head to be adjusted, the head controller 6H drives the motor corresponding to the head to be adjusted to activate the first actuator 5A of the head to be adjusted so that the head rotates in the width direction by the angle calculated in step S30. When step S60 is completed, the CPU 210 of PC200 proceeds to step S70. On the other hand, if the CPU 210 of PC200 receives input indicating that angle adjustment in the width direction is not necessary (step S50: NO), the CPU 210 of PC200 proceeds to step S70.

[0047] If the CPU 210 of PC200 receives input indicating that adjustment of the widthwise position is necessary (step S70: YES), the CPU 210 of PC200 performs a widthwise position adjustment on the head to be adjusted (step S80). Specifically, the CPU 210 of PC200 sends a position adjustment instruction to the head controller 6H. Upon receiving the position adjustment instruction, the head controller 6H drives the motor corresponding to the head to be adjusted to activate the second actuator 5B of the head to be adjusted so that the head moves in the widthwise direction according to the widthwise distance calculated in step S30. When step S80 is completed, the CPU 210 of PC200 proceeds to step S90. On the other hand, if the CPU 210 of PC200 receives input indicating that adjustment of the widthwise position is not necessary (step S70: NO), the CPU 210 of PC200 proceeds to step S90.

[0048] If the CPU 210 of PC200 receives input indicating that adjustment of the transport direction position is necessary (step S90: YES), the CPU 210 of PC200 adjusts the discharge timing of the head to be adjusted (step S100). Specifically, the CPU 210 of PC200 sends an instruction to the head controller 6H to adjust the discharge timing of the head to be adjusted. Upon receiving the instruction to adjust the discharge timing of the head to be adjusted, the head controller 6H adjusts the discharge timing of the head to be adjusted according to the transport direction distance calculated in step S30. When step S100 is completed, the CPU 210 of PC200 proceeds to step S110. On the other hand, if the CPU 210 of PC200 receives input indicating that adjustment of the transport direction position is not necessary (step S90: NO), the CPU 210 of PC200 proceeds to step S110.

[0049] If the CPU 210 of PC200 receives input indicating that density adjustment is necessary (step S110: YES), the CPU 210 of PC200 adjusts the drive voltage for the head to be adjusted (step S120). Specifically, the CPU 210 of PC200 sends a density adjustment instruction for the head to be adjusted to the head controller 6H. Upon receiving the density adjustment instruction for the head to be adjusted, the head controller 6H adjusts the drive voltage for the head to be adjusted according to the density difference calculated in step S30. Once step S120 is completed, the CPU 210 of PC200 proceeds to step S130. On the other hand, if the CPU 210 of PC200 receives input indicating that density adjustment is not necessary (step S110: NO), the CPU 210 of PC200 proceeds to step S130.

[0050] In step S130, the CPU 210 of PC200 sends a test pattern print instruction to the head controller 6H. Upon receiving the test pattern print instruction, the head controller 6H drives all 10 heads 1 included in the line head 10H to eject ink droplets, thereby printing 10 identical test patterns TP arranged in the width direction onto the medium M being transported in the transport direction. If the result in steps S50, S70, S90, and S110 is NO, then no adjustments are needed for the head to be adjusted, and steps S130 and the subsequent step S140 are not performed, and the flow is terminated.

[0051] Then, in step S130, the user visually checks the reprinted test pattern and inputs whether sufficient image quality was obtained via the input unit 240 of the PC200. If the CPU 210 of the PC200 receives input that sufficient image quality was not obtained (S140: NO), the CPU 210 of the PC200 returns to step S20. On the other hand, if the CPU 210 of the PC200 receives input that sufficient image quality was obtained (S140: YES), the CPU 210 of the PC200 terminates the flow.

[0052] Next, we will explain in detail the process of test pattern analysis in step S30.

[0053] (Angle calculation) First, the CPU210 of the PC200 uses the first pattern P1 included in the test pattern TP to be adjusted to calculate the angle of the head to be adjusted relative to the width direction on a virtual plane including the nozzle surface NS. The method for calculating this angle will be explained below with reference to Figures 7(a) to 7(c). In Figures 7(a) to 7(c), it is assumed that the second head from the left, head 1, is the head to be adjusted.

[0054] Figure 7(a) shows the case where the head to be adjusted is not tilted with respect to the width direction, that is, the angle of the head to be adjusted with respect to the width direction is [0 rad]. Figure 7(b) shows the case where the head to be adjusted is tilted counterclockwise with respect to the width direction, that is, the angle of the head to be adjusted with respect to the width direction is θ [rad]. Figure 7(c) shows the case where the head to be adjusted is tilted clockwise with respect to the width direction, that is, the angle of the head to be adjusted with respect to the width direction is -θ [rad].

[0055] In Figures 7(a) to 7(c), nozzles N1 and N2 are included in the head to be adjusted, and their positions in the width direction and transport direction are different from each other. Vertical lines L1 are formed by ink droplets continuously ejected from nozzle N1, and vertical lines L2 are formed by ink droplets continuously ejected from nozzle N2. Vertical lines L1 and L2 constitute the first pattern P1, but other vertical lines that constitute the first pattern P1 are omitted in Figures 7(a) to 7(c).

[0056] Here, as shown in Figure 7(a), the distance d between nozzle N1 and nozzle N2, and the distance d1 in the width direction between vertical lines L1 and vertical lines L2 are predetermined during the design of the head 1. Furthermore, the initial angle of the vector from nozzle N1 to nozzle N2 with respect to the width direction is also predetermined during the design of the head 1.

[0057] Therefore, for example, as shown in Figure 7(b), if the head to be adjusted is tilted counterclockwise with respect to the width direction, we need to find the angle θ that satisfies cos(θ - initial angle) = d / d2. Here, as mentioned above, the initial angle and distance d are predetermined values, and the distance d2 can be determined by analyzing the image data acquired from the scanner.

[0058] On the other hand, as shown in Figure 7(c), if the head to be adjusted is tilted clockwise with respect to the width direction, it is sufficient to find the angle θ that satisfies cos((-θ)-initial angle)=d / d3. Here, as described above, the initial angle and distance d are predetermined values, and the distance d3 can be determined by analyzing the image data acquired from the scanner. In the above description, nozzle N1 is an example of the first nozzle of the present invention, and nozzle N2 is an example of the second nozzle of the present invention. Also, vertical line L1 is an example of the first line of the present invention, and vertical line L2 is an example of the second line of the present invention.

[0059] (Calculation of distance in the width direction) Next, the CPU210 of PC200 calculates the distance in the width direction between the test pattern TP to be adjusted and the reference test pattern TP. Here, if the head to be adjusted is tilted with respect to the width direction, the position in the width direction of each nozzle N included in the head to be adjusted will be shifted compared to the position in the width direction of each nozzle N when the head to be adjusted is not tilted with respect to the width direction. For this reason, if the head to be adjusted is tilted with respect to the width direction, the positions in the width direction of the multiple vertical lines that make up the vertical pattern P21 will also be shifted compared to the positions in the width direction of the multiple vertical lines that make up the vertical pattern P21 when the head to be adjusted is not tilted with respect to the width direction.

[0060] Therefore, the CPU 210 of the PC200 corrects the data of the vertical pattern P21 included in the test pattern TP to be adjusted, which was read in step S20, to the data of the vertical pattern P21 that would be formed if the head to be adjusted was not tilted in the width direction. Specifically, the CPU 210 of the PC200 uses the angle of the head to be adjusted relative to the width direction and the rotation matrix, calculated as described above, to calculate the widthwise coordinates of each nozzle N when the head to be adjusted is not tilted in the width direction. Then, the CPU 210 of the PC200 corrects the data of the vertical pattern P21 based on the calculated widthwise coordinates of each nozzle N, and uses the corrected vertical pattern P21 data and the data of the vertical pattern P21 included in the reference test pattern TP to calculate the widthwise distance. In other words, the CPU 210 of the PC200 can calculate the widthwise distance between the test pattern TP to be adjusted and the reference test pattern TP, taking into account the widthwise positional shift that occurs when adjusting the angle of the head to be adjusted relative to the width direction. The distance in the width direction between the corrected vertical pattern P21 and the vertical pattern P21 included in the reference test pattern TP is an example of the first distance of the present invention.

[0061] (Calculation of distance in the transport direction) Next, the CPU210 of PC200 calculates the distance in the transport direction between the test pattern TP to be adjusted and the reference test pattern TP. Here, if the head to be adjusted is tilted with respect to the width direction, the transport direction position of each nozzle N included in the head to be adjusted will also be shifted compared to the transport direction position of each nozzle N when the head to be adjusted is not tilted with respect to the width direction. Therefore, when the head to be adjusted is tilted with respect to the width direction, each horizontal line constituting the horizontal pattern P22 will be tilted compared to each horizontal line constituting the horizontal pattern P22 when the head to be adjusted is not tilted with respect to the width direction.

[0062] Therefore, the CPU 210 of the PC200 corrects the lateral pattern P22 data included in the test pattern TP to be adjusted, which was read in step S20, to the lateral pattern P22 data that would be formed if the head to be adjusted was not tilted with respect to the width direction. Specifically, the CPU 210 of the PC200 uses the angle of the head to be adjusted with respect to the width direction and the rotation matrix, calculated as described above, to calculate the coordinates of each nozzle N in the transport direction when the head to be adjusted is not tilted with respect to the width direction. Then, the CPU 210 of the PC200 corrects the lateral pattern P22 data based on the calculated coordinates of each nozzle N in the transport direction, and uses the corrected lateral pattern P22 data and the lateral pattern P22 data included in the reference test pattern TP to calculate the distance in the transport direction between the test pattern TP to be adjusted and the reference test pattern TP, taking into account the positional shift in the transport direction due to the adjustment of the angle of the head to be adjusted with respect to the width direction. The distance in the transport direction between the corrected lateral pattern P22 and the lateral pattern P22 included in the reference test pattern TP is an example of the second distance of the present invention.

[0063] When calculating the distance in the transport direction between the corrected horizontal pattern P22 and the horizontal pattern P22 included in the reference test pattern, the CPU 210 of the PC 200 uses, for example, the first part R1 and the second part R2 shown in Figure 8. Specifically, the average value of the position coordinates in the transport direction of the first part R1 and the average value of the position coordinates in the transport direction of the second part R2 are used. The first part R1 is a portion of the horizontal ruled line HL3 that constitutes the corrected horizontal pattern P22, located at a predetermined distance from the end adjacent to the reference test pattern TP. The second part R2 is a portion of the horizontal ruled line HL3 that constitutes the horizontal pattern P22 of the reference test pattern TP, located at a predetermined distance from the end adjacent to the test pattern TP to be adjusted. The horizontal ruled line HL3 that constitutes the corrected horizontal pattern P22 is an example of the third ruled line of the present invention. The horizontal ruled line HL3 that constitutes the horizontal pattern P22 of the reference test pattern TP is an example of the fourth ruled line of the present invention. The right and left ends of the horizontal ruled lines HL3 constituting the corrected horizontal pattern P22 in Figure 8 are examples of the first and second ends of the present invention, respectively. The left and right ends of the horizontal ruled lines HL3 constituting the horizontal pattern P22 of the reference test pattern TP in Figure 8 are examples of the third and fourth ends of the present invention, respectively.

[0064] (Calculation of print density difference) Furthermore, the CPU210 of the PC200 calculates the difference in print density between the test pattern TP to be adjusted and the reference test pattern TP. The difference in print density between the test pattern TP to be adjusted and the reference test pattern TP is calculated based on the print density of the third pattern P3 contained in each. Here, when measuring the print density of the third pattern P3 contained in the test pattern TP to be adjusted, the CPU210 of the PC200 changes the width of the reading range per frame of the moving average according to the angle of the head to be adjusted relative to the width direction, which is calculated as described above. Specifically, if the angle of the head to be adjusted relative to the width direction exceeds a predetermined range (for example, -(π / 180)[rad] or more and (π / 180)[rad] or less), the reading range per frame is set to the first range. On the other hand, if the angle of the head to be adjusted relative to the width direction is within the predetermined range (for example, -(π / 180)[rad] or more and (π / 180)[rad] or less), the reading range per frame is set to the second range, which is narrower than the first range.

[0065] When the angle of the head to be adjusted with respect to the width direction exceeds a predetermined range, that is, when the angle is not adjusted, the distance between nozzles N is not constant, and multiple streaks extending in the transport direction are likely to occur in the third pattern P3. For this reason, when measuring the density of the third pattern P3, the reading range per frame when performing a moving average is set to the first range. On the other hand, when the angle of the head to be adjusted with respect to the width direction is within a predetermined range, that is, when the angle is adjusted, the distance between nozzles N is almost constant, and multiple streaks extending in the transport direction are less likely to occur in the third pattern P3. For this reason, when measuring the density of the third pattern P3, the reading range per frame when performing a moving average is set to the second range, which is narrower than the first range. Streaks are noise in density measurement. When multiple streaks are likely to occur, noise is likely to occur, so in order to reduce the effect of noise, the reading range per frame when performing a moving average is set to the first range, which is wider than the second range. On the other hand, if multiple streaks are unlikely to occur, noise is less likely to occur and the image is less affected by noise. Therefore, the reading range per frame when performing the moving average is set to a second range, which is narrower than the first range.

[0066] Furthermore, when measuring the print density of the third pattern P3 included in the test pattern TP to be adjusted, the CPU 210 of the PC 200 changes the range for measuring the print density according to the distance in the width direction between the vertical pattern P21 read in step S20 and the vertical pattern P21 of the reference test pattern TP. Specifically, if the distance in the width direction between the vertical pattern P21 read in step S20 and the vertical pattern P21 of the reference test pattern TP is not 0, the range for acquiring the moving average frame is set to the third range. On the other hand, if the distance in the width direction between the vertical pattern P21 read in step S20 and the vertical pattern P21 of the reference test pattern TP is 0, the range for acquiring the moving average frame is set to the fourth range, which is different from the third range. Here, the third range is the range of the rectangular third pattern P3 that is a predetermined distance in the width direction from the side closest to the reference test pattern TP, and the fourth range is the range of the rectangular third pattern P3 that includes the side closest to the reference test pattern TP, and includes the entirety of the third range.

[0067] If the distance in the width direction between the vertical pattern P21 read in step S20 and the vertical pattern P21 of the reference test pattern TP is not zero, that is, if the distance in the width direction has not been adjusted, then the third pattern P3 of the test pattern TP to be adjusted and the third pattern P3 of the reference test pattern TP are either overlapping or separated in the width direction. If the third pattern P3 of the test pattern TP to be adjusted and the third pattern P3 of the reference test pattern TP overlap, the print density in the overlapping area will be darker, resulting in black streaks. On the other hand, if the third pattern P3 of the test pattern TP to be adjusted and the third pattern P3 of the reference test pattern TP are separated, white streaks will appear between them. Since black and white streaks are noise in the measurement of print density, it is desirable to eliminate the influence of noise when measuring print density. The black and white streaks occur within a range that is a predetermined distance in the width direction from the side of the rectangular third pattern P3 of the test pattern TP that is closest to the reference test pattern TP. Here, the predetermined distance is the larger of the maximum distance in the width direction of the overlapping portion when the third pattern P3 of the test pattern TP to be adjusted and the third pattern P3 of the reference test pattern TP overlap, and the maximum distance in the width direction when they are separated. Therefore, if the distance in the width direction between the vertical pattern P21 read in step S20 and the vertical pattern P21 of the reference test pattern TP is not 0, the print density in the third range is measured so as not to be affected by black or white streaks.

[0068] On the other hand, if the distance in the width direction between the vertical pattern P21 read in step S20 and the vertical pattern P21 of the reference test pattern TP is 0, that is, if the distance in the width direction is adjusted, then the third pattern P3 of the adjusted test pattern TP and the third pattern P3 of the reference test pattern TP do not overlap with each other and are not separated in the width direction. Therefore, no black or white streaks occur between them. Thus, if the distance in the width direction between the vertical pattern P21 read in step S20 and the vertical pattern P21 of the reference test pattern TP is 0, the print density in the fourth range is measured.

[0069] Next, we will specifically explain the widthwise position adjustment in step S80, the discharge timing adjustment in step S100, and the drive voltage adjustment in step S120.

[0070] First, if one of the ten heads 1 included in the line head 10H is designated as the head to be adjusted, then, as described above, only the one head 1 adjacent to the head to be adjusted becomes the reference head 1.

[0071] Then, as a result of step S30, we assume that the distance in the width direction between the corrected test pattern TP1 and the reference test pattern TP2 is d1 and the distance in the transport direction is d2, as shown in Figure 9. In this case, in step S80, the head controller 6H drives the motor corresponding to the head to be adjusted to activate the actuator 5 of the head to be adjusted so that the head to be adjusted moves by a distance d1 in the width direction. To explain using the specific example in Figure 9, the vertical lines of the test pattern TP1 to be adjusted are shifted to the left by a distance d1 relative to the vertical lines of the reference test pattern TP2. That is, the head to be adjusted is shifted to the left by a distance d1 relative to the reference head 1. Therefore, the head controller 6H drives the motor to activate the actuator 5B so that the head to be adjusted moves to the right by a distance d1. Also, in step S100, the head controller 6H adjusts the discharge timing of the head to be adjusted so that the position of the test pattern TP1 in the transport direction is the same as the position of the reference test pattern TP2 in the transport direction. As illustrated in the specific example in Figure 9, the horizontal lines of the test pattern TP1 to be adjusted are shifted upstream in the transport direction by a distance d2 relative to the horizontal lines of the reference test pattern TP2. In other words, the ejection timing of the head to be adjusted is earlier than that of the reference head 1 by a time equivalent to a distance d2. Therefore, the head controller 6H delays the ejection timing of the head to be adjusted by a time equivalent to a distance d2. Furthermore, if a density difference is found between the test pattern TP1 to be adjusted and the reference test pattern TP2 as a result of step S30, in step S120, the head controller 6H adjusts the drive voltage of the head to be adjusted so that the density of the test pattern TP1 becomes equal to the density of the reference test pattern TP2. At this time, the head controller 6H adjusts the drive voltage of the head to be adjusted by referring to a mapping table of voltage values ​​and density values, for example, which is pre-stored in the ROM 62. Note that when printing the test pattern in step S10 after replacing the head to be adjusted, the drive voltage of the head to be adjusted is set to the same value as the drive voltage of the reference head 1.

[0072] Next, we will explain the case where one of the ten heads 1 included in the line head 10H, located outside the widthwise end, is designated as the head to be adjusted. In this case, as described above, the two heads 1 located on either side of the head to be adjusted become the reference heads 1.

[0073] If there are two reference heads 1, in step S30, the distance in the width direction, the distance in the transport direction, and the density difference between the two reference test patterns TP printed by the two reference heads 1 are determined. For example, let's assume that the distance in the width direction between the two reference test patterns TP2 and TP3 is d, as shown in Figure 10. In this case, it is desirable that the reference test pattern TP2, the test pattern to be adjusted TP1, and the reference test pattern TP3 are printed at equal intervals in the width direction. Therefore, in step S80, the head controller 6H determines the target position of the head to be adjusted. Specifically, it determines a target position where the distance from one reference head 1 to the target position is equal to the distance from the other reference head 1 to the target position. Then, the head controller 6H drives the motor corresponding to the head to be adjusted to activate the actuator 5 of the head to be adjusted so that the head to be adjusted moves to the target position. This will be explained with a specific example in Figure 10. In Figure 10, the position in the width direction of a predetermined vertical line in the test pattern TP1 to be adjusted is X1 before adjustment, and the position in the width direction after adjustment is X. Also, the positions in the width direction of the predetermined vertical lines in the reference test patterns TP2 and TP3 are X2 and X3, respectively. Before adjustment, the distance from position X2 to position X1 is longer than the distance from position X3 to position X1. In other words, before adjustment, the head to be adjusted is shifted to the right by |X1-X| relative to the target position where the distance from the two reference heads 1 is equal. Therefore, the head controller 6H drives the motor corresponding to the head to be adjusted to move the head to be adjusted to the left by |X1-X|, thereby activating the actuator 5 of the head to be adjusted.

[0074] Furthermore, in step S100, the head controller 6H determines the target discharge timing of the head to be adjusted in order to make the distance in the transport direction from the reference test pattern TP2 to the corrected test pattern TP1 equal to the distance in the transport direction from the reference test pattern TP3 to the corrected test pattern TP1. This will be explained with a specific example in Figure 10. In Figure 10, let Y1 be the position in the transport direction of a predetermined horizontal line of the test pattern TP1 to be adjusted before adjustment, and Y be the position in the transport direction after adjustment. Also, let Y2 and Y3 be the positions in the transport direction of the predetermined horizontal lines of the reference test patterns TP2 and TP3, respectively. Before adjustment, the distance from position Y2 to position Y1 is shorter than the distance from position Y3 to position Y1. In other words, position Y1 is shifted upstream in the transport direction by a distance of |Y-Y1| relative to position Y, where the distance from the horizontal lines of the reference test patterns TP2 and TP3 is equal. That is, the head to be adjusted has a discharge timing that is earlier than the ideal discharge timing by a time corresponding to the distance of |Y-Y1|. Therefore, the head controller 6H delays the ejection timing of the head to be adjusted by a time equivalent to the distance |Y-Y1|.

[0075] Furthermore, in step S120, the head controller 6H determines the target drive voltage value for the head to be adjusted in order to equalize the density difference between the reference test pattern TP2 and the test pattern TP1 to be adjusted, and the density difference between the test pattern TP1 to be adjusted and the reference test pattern TP3. Specifically, the head controller 6H determines the target drive voltage value for the head to be adjusted by referring to a mapping table of voltage values ​​and density values ​​pre-stored in, for example, the ROM 62, so that the density of the test pattern TP1 to be adjusted becomes the average density of the density of the reference test pattern TP2 and the density of the reference test pattern TP3. For example, if the density of the reference test pattern TP2 is 62 and the density of the reference test pattern TP3 is 65, the head controller 6H determines the target drive voltage value for the head to be adjusted so that the density of the test pattern to be adjusted becomes 63.5, which is the average value of 62 and 65. Then, the head controller 6H adjusts the drive voltage of the head to be adjusted to the target drive voltage value. Furthermore, when printing a test pattern in step S10 after replacing the head to be adjusted, the drive voltage of the head to be adjusted is set to the average value of the drive voltages of the two reference heads 1.

[0076] Even if n (n≧2) consecutive heads 1 located outside the widthwise ends of the 10 heads 1 included in the line head 10H are designated as heads to be adjusted, the same adjustment can be performed as when there is only one head to be adjusted.

[0077] In other words, in step S80, the head controller 6H determines n target positions that divide the widthwise distance from one reference head 1 to the other reference head 1 into (n+1) equal parts. Then, the head controller 6H operates the n actuators 5 of each of the n heads to be adjusted so that each of the n heads to be adjusted moves to the n target positions.

[0078] Furthermore, in step S100, the head controller 6H determines the target discharge timings for the n heads to be adjusted so that the n test patterns to be adjusted are positioned at n target positions, each of which divides the transport distance from the reference test pattern TP2 to the reference test pattern TP3 into (n+1) equal parts. The head controller 6H then shifts the discharge timings of the n heads to be adjusted to the n target discharge timings.

[0079] Furthermore, in step S120, the head controller 6H determines the target drive voltage value for each of the n heads to be adjusted such that the density of each of the n test patterns to be adjusted is a value that divides the difference between the density of the reference test pattern TP2 and the density of the reference test pattern TP3 into (n+1) equal parts. In this case, the head controller 6H determines the target drive voltage value for each of the n heads to be adjusted by referring to a mapping table of voltage values ​​and density values ​​that is pre-stored in, for example, the ROM 62. For example, suppose there are two heads to be adjusted, and the density of the reference test pattern TP2 is 62 and the density of the reference test pattern TP3 is 65. In this case, the head controller 6H determines the target voltage values ​​for the two heads to be adjusted such that the densities of the two test patterns to be adjusted are 63 and 64 (two values ​​that divide the density difference between 65 and 62 into three equal parts). Then, the head controller 6H adjusts the drive voltage of each of the n heads to be adjusted to the n target drive voltage values. Furthermore, after replacing the heads with n adjustment targets, when printing a test pattern in step S10, the drive voltage of the n adjustment target heads is set to the average voltage value of the drive voltages of the two reference heads 1.

[0080] According to the embodiments described above, the procedure for adjusting the position of the head to be adjusted is simplified, and the position of the head to be adjusted can be appropriately adjusted while taking into account the positions of heads adjacent to the head to be adjusted.

[0081] Furthermore, the distance in the width direction and the distance in the transport direction between the head to be adjusted and the adjacent head 1 are calculated, taking into account the angle of the head to be adjusted with respect to the width direction. Therefore, the position of the head to be adjusted can be adjusted more appropriately compared to when the angle of the head to be adjusted with respect to the width direction is not considered.

[0082] Furthermore, the range for measuring print density is changed according to the angle of the head being adjusted relative to the width direction, and the distance in the width direction between the corrected test pattern TP being adjusted and the reference test pattern TP. This allows for appropriate measurement of the print density of both the test pattern TP being adjusted and the reference test pattern TP. As a result, the drive voltage of the head being adjusted can be appropriately adjusted.

[0083] Furthermore, if the head to be adjusted is located anywhere other than the edge in the width direction, the position in the width direction, the position in the transport direction, and the density of the test pattern to be adjusted can be adjusted so that they change in steps from one reference test pattern TP to the other reference test pattern TP. This allows for obtaining good image quality.

[0084] The embodiments described above are illustrative in all respects and not restrictive. Not all of the configurations shown in the embodiments are essential, and configurations can be modified or omitted as needed.

[0085] In the above embodiment, the scanner 300 was electrically connected to the PC 200 via the input / output interface 260, but this is not limited to this. For example, the printer 100 may have a CIS (contact image sensor). In this case, a PC for storing image data read by the CIS may be provided and electrically connected to the printer 100 and the PC 200.

[0086] In the above embodiment, in steps S10 and S80, all 10 heads included in the line head were driven to print 10 identical test patterns TP on the medium M, but this is not limited to this. For example, only the head to be adjusted and the reference head 1 may be driven to print only the test pattern to be adjusted TP and the reference test pattern TP on the medium M.

[0087] In the above embodiment, the number and arrangement of heads 1 included in each of the line heads 10A to 10H can be changed as appropriate. Furthermore, the number and arrangement of nozzles N included in each head 1 can also be changed as appropriate.

[0088] Furthermore, in the above embodiment, white, yellow, orange, magenta, violet, cyan, and black inks were ejected from the line heads 10A to 10H, but the invention is not limited to these, and inks of any appropriate color may be ejected.

[0089] In the above embodiment, roll paper was used as the medium M, but any medium of an appropriate material can be used as needed. For example, the medium M may be a roll of resin film or cloth. [Explanation of Symbols]

[0090] 1. Droplet dispensing head 2 Flow channel members 3. Piezoelectric actuator 4 Driver ICs 5A First Actuator 5B Second Actuator 6A~6H Head Controller 10A~10H Line Head 20 Conveying device 100 Printers 200 PC 300 Scanners 1000 Printing Systems

Claims

1. A method for adjusting a droplet ejection head, performed by a controller in a printing system, The aforementioned printing system, A line head comprising a plurality of droplet dispensing heads, each of the plurality of droplet dispensing heads having a dispensing surface extending in a first direction and a second direction perpendicular to the first direction, and the plurality of droplet dispensing heads being arranged along the first direction, A first actuator rotates each of the plurality of droplet dispensing heads within the line head along a virtual plane including the dispensing surface in the first direction, A second actuator moves each of the plurality of droplet dispensing heads along the first direction within the line head, Equipped with a scanner, The adjustment method described above is: The line head is used to discharge droplets onto a single medium being transported in the second direction from the head to be adjusted, thereby forming a first pattern on the medium that indicates the angle of the head to be adjusted relative to the first direction on the virtual surface, and a second pattern that indicates the position of the head to be adjusted in the first and second directions. The liquid droplet is discharged onto the single medium being transported in the second direction from a reference head adjacent to the head to be adjusted, which is included in the line head, thereby forming a first pattern on the medium that indicates the angle of the reference head with respect to the first direction on the virtual plane, and a second pattern that indicates the position of the reference head in the first and second directions. The scanner is made to read the first pattern and the second pattern formed by the adjustment target head, and the first pattern and the second pattern formed by the reference head. The angle of the head to be adjusted is calculated from the first pattern obtained by the head to be adjusted as read by the scanner, Based on the calculated angle, the position of the second pattern of the head to be adjusted in the first and second directions is corrected. To calculate the first distance, which is the distance in the first direction, and the second distance, which is the distance in the second direction, between the second pattern using the reference head and the second pattern using the corrected adjustment target head. The first actuator is to rotate the head to be adjusted by the calculated angle, In accordance with the first distance, the adjustment target head is moved by the second actuator along the first direction without moving the reference head, An adjustment method comprising adjusting the discharge timing from the head to be adjusted without changing the discharge timing from the reference head, according to the second distance.

2. The head to be adjusted includes a first nozzle and a second nozzle whose positions in the first direction and the positions in the second direction are different from each other. The first pattern formed by the head to be adjusted includes a first scribe line extending in the second direction formed by ejecting the droplet multiple times from the first nozzle, and a second scribe line extending in the second direction formed by ejecting the droplet multiple times from the second nozzle. The adjustment method according to claim 1, wherein the controller calculates the angle of the head to be adjusted with respect to the first direction based on the distance in the first direction between the first line and the second line in the first pattern read by the head to be adjusted by the scanner.

3. Each of the head to be adjusted and the reference head includes a plurality of nozzles, each having a different position in the first direction. The second pattern formed by the head to be adjusted includes a third line formed by discharging the droplet once from each of the plurality of nozzles of the head to be adjusted, The second pattern formed by the reference head includes a fourth line formed by discharging the droplet once from each of the plurality of nozzles of the reference head. The third ruled line has a first end and a second end that is further from the fourth ruled line than the first end. The fourth ruled line has a third end and a fourth end that is further from the third ruled line than the third end. The adjustment method according to claim 1, wherein the controller calculates the second distance based on the distance in the second direction between a first portion of the second pattern of the corrected head to be adjusted, which is located at a predetermined distance from the first end of the third line, and a second portion of the fourth line, which is located at a predetermined distance from the third end.

4. The adjustment method described above is: From each of the head to be adjusted and the reference head, droplets are ejected onto the medium to form a third pattern on the medium for measuring the print density. The method further includes causing the scanner to read the third pattern formed by the head to be adjusted, The adjustment method according to claim 1, wherein the controller determines, according to the angle of the head to be adjusted with respect to the first direction, whether to measure the print density of a first range included in the third pattern read by the head to be adjusted, or to measure the print density of a second range included in the third pattern read by the head to be adjusted, and which is narrower than the first range.

5. The adjustment method according to claim 4, wherein the controller measures the print density in a first range when the angle of the head to be adjusted with respect to the first direction exceeds a predetermined range.

6. The adjustment method according to claim 4, wherein the controller measures the print density in the second range when the angle of the head to be adjusted with respect to the first direction is within a predetermined range.

7. The adjustment method described above is: From each of the head to be adjusted and the reference head, droplets are ejected onto the medium to form a rectangular third pattern on the medium for measuring the print density. The method further includes causing the scanner to read the third pattern formed by the head to be adjusted, The third pattern of the head to be adjusted has a first side and a second side opposite to the first side. The first side is closer to the third pattern by the reference head than the second side. The controller determines, according to the first distance, whether to measure the print density of a third range included in the third pattern by the read head to be adjusted, or to measure the print density of a fourth range that is included in the third pattern by the read head to be adjusted, but is different from the third range. The third range is located a predetermined distance away in the first direction from the first side of the third pattern formed by the head to be adjusted, The adjustment method according to claim 1, wherein the fourth range includes the first side of the third pattern by the head to be adjusted.

8. The adjustment method according to claim 7, wherein the controller measures the print density in the third range when the first distance is not zero.

9. The adjustment method according to claim 7, wherein the controller measures the print density in the fourth range when the first distance is 0.

10. A printing system, A line head comprising a plurality of droplet dispensing heads, each of the plurality of droplet dispensing heads having a dispensing surface extending in a first direction and a second direction perpendicular to the first direction, and the plurality of droplet dispensing heads being arranged along the first direction, A first actuator rotates each of the plurality of droplet dispensing heads within the line head along a virtual plane including the dispensing surface in the first direction, A second actuator moves each of the plurality of droplet dispensing heads along the first direction within the line head, Scanner and The system comprises the line head, the first actuator, the second actuator, and the scanner, and an electrically connected controller. The aforementioned controller, A droplet is discharged from the head to be adjusted into a medium conveyed in the second direction, which is included in the line head, thereby forming a first pattern on the medium that indicates the angle of the head to be adjusted relative to the first direction on the virtual surface, and a second pattern that indicates the position of the head to be adjusted in the first and second directions. A droplet is discharged onto a single medium being transported in the second direction from a reference head adjacent to the head to be adjusted, which is included in the line head, thereby forming a first pattern on the medium that indicates the angle of the reference head with respect to the first direction on the virtual plane, and a second pattern that indicates the position of the reference head in the first and second directions. The scanner reads the first pattern and the second pattern formed by the adjustment target head, and the first pattern and the second pattern formed by the reference head. From the first pattern obtained by the head to be adjusted as read by the scanner, the angle of the head to be adjusted is calculated. Based on the calculated angle, the position of the second pattern of the head to be adjusted in the first and second directions is corrected. The first distance, which is the distance in the first direction, and the second distance, which is the distance in the second direction, are calculated between the second pattern using the reference head and the second pattern using the corrected adjustment target head. The first actuator rotates the head to be adjusted by the calculated angle, In accordance with the first distance, the second actuator moves the head to be adjusted along the first direction without moving the reference head. A printing system that adjusts the ejection timing from the head to be adjusted without changing the ejection timing from the reference head, according to the second distance.

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