Image formation apparatus, adjustment method and program

Abstract

To provide an image formation apparatus, adjustment method, and program capable of accurately correcting the landing position of discharged ink and suppressing quality deterioration of a formed image.SOLUTION: An image formation apparatus includes: an ink jet head that discharges ink droplets onto a recording medium; and a control unit that performs adjustment processing including a first adjustment which adjusts a drive waveform of the ink jet head on the basis of a landing position of ink of a first pattern image formed by making two ink droplets with different discharge amounts discharged at intervals greater than or equal to a predetermined interval, land on the recording medium, and a second adjustment which is performed after the first adjustment, and adjusts the drive waveform on the basis of a landing position of ink droplets of a second pattern image formed by making the two ink droplets discharged in multiple landing patterns obtained by combining multiple discharge conditions, land on the recording medium.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to an image forming apparatus, an adjustment method, and a program. [Background technology]

[0002] Conventionally, there is known an inkjet type image forming apparatus (hereinafter referred to as "inkjet image forming apparatus") that ejects ink onto a recording medium such as paper to form an image on the recording medium. In an inkjet image forming apparatus, when a voltage is applied to an inkjet head (hereinafter referred to as "head") having a plurality of nozzles to eject ink from the nozzles, meniscus vibration, which is temporal interference caused by a previous ejection, may remain. If meniscus vibration remains, the ejection of ink from the head may become unstable, or the ink droplet speed may fluctuate.

[0003] In particular, in recent years, when there is a demand for faster image formation and higher image quality, the effects on image quality caused by droplets ejected from multiple nozzles, not just the previous ejection from the same nozzle, and the resulting deviation in the landing position cannot be ignored. Therefore, in order to improve image quality, it is necessary to correct the landing position of the ink on the recording medium in accordance with the state of each head, such as individual differences and the usage environment.

[0004] For example, Patent Document 1 discloses a liquid ejection device that accurately corrects changes in the volume and landing position of ejected liquid droplets. This liquid ejection device adds a predetermined correction amount to the ejection waveform when ink droplets are ejected in an ejection pattern that may cause meniscus vibration.

[0005] Patent Document 2 discloses a droplet ejection device that suppresses deviations in the landing positions of ejected droplets. This droplet ejection device adjusts the application timing of a non-ejecting micro-driving waveform that is applied before the driving waveform, based on the positions of the first and second dots in a test image formed by successively applying driving waveforms for ejecting droplets of the same size. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-159643 A [Patent Document 2] JP 2019-177690 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the liquid ejection device described in Patent Document 1, the amount of correction required may change depending on the state of the head, such as individual differences, the usage environment, or durability, etc. Therefore, depending on the state of the head, it is difficult to accurately correct the droplet volume and landing position of the ejected liquid.

[0008] Furthermore, the droplet ejection device described in Patent Document 2 does not take into consideration cases where droplets of different sizes are ejected, cases where droplets are ejected corresponding to dots that are sufficiently separated, etc. Therefore, it is difficult to realize high speed and high image quality when forming various images.

[0009] The present disclosure has been made in consideration of the problems in the above-mentioned conventional technology, and aims to provide an image forming apparatus, an adjustment method, and a program that can accurately correct the landing position of ejected ink and suppress deterioration in the quality of the formed image. [Means for solving the problem]

[0010] The image forming apparatus according to the present disclosure includes: An inkjet head that ejects ink droplets onto a recording medium; a control unit that performs an adjustment process including a first adjustment for adjusting a drive waveform of the inkjet head based on landing positions of the ink droplets of a first pattern image formed by landing two of the ink droplets, which are different in amount and are ejected at an interval of a predetermined interval or more, on the recording medium, and a second adjustment that is performed after the first adjustment and adjusts the drive waveform based on landing positions of the ink droplets of a second pattern image formed by landing two of the ink droplets, which are ejected in a plurality of landing patterns obtained by combining a plurality of ejection conditions, on the recording medium; Equipped with.

[0011] In addition, the adjustment method according to the present disclosure includes: adjusting a driving waveform of the inkjet head based on a landing position of the ink droplets of a first pattern image formed by landing two ink droplets, the ink droplets having different ejection amounts, on the recording medium, the ink droplets being ejected from an inkjet head at an interval of at least a predetermined interval; After the adjustment, the drive waveform is adjusted based on the landing positions of the ink droplets of a second pattern image formed by landing two of the ink droplets on the recording medium in a plurality of landing patterns obtained by combining a plurality of ejection conditions.

[0012] Furthermore, the program according to the present disclosure includes: The above adjustment method is executed by a computer. Effect of the Invention

[0013] According to the present disclosure, it is possible to accurately correct the landing position of ejected ink and suppress deterioration in the quality of formed images. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of an inkjet printer according to this embodiment. [Diagram 2]FIG. 2 is a block diagram showing the main components of a control system of the inkjet printer. [Diagram 3] FIG. 3 is a functional block diagram illustrating an example of the configuration of the control unit. [Figure 4] FIG. 4 is a schematic diagram for explaining an example of the first driving waveform. [Diagram 5] FIG. 5 is a schematic diagram for explaining an example of the second driving waveform. [Figure 6] FIG. 6 is a schematic diagram for explaining an example of the third driving waveform. [Figure 7] FIG. 7 is a flowchart showing an example of the flow of the first adjustment process by the inkjet printer according to the present embodiment. [Figure 8] FIG. 8 is a schematic diagram showing an example of a first pattern image used in the first adjustment processing. [Figure 9] FIG. 9 is a flowchart showing an example of the flow of the second adjustment process by the inkjet printer according to the present embodiment. [Figure 10] FIG. 10 is a schematic diagram for explaining the ink droplet ejection conditions in the second adjustment process. [Figure 11] FIG. 11 is a schematic diagram showing an example of the second pattern image used in the second adjustment processing. [Figure 12] FIG. 12 is a flowchart showing an example of the flow of the second adjustment process according to the modification of the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and various modifications are possible without departing from the spirit of the present disclosure. In addition, in each drawing, the same reference numerals are used to denote the same or equivalent parts, and this is common throughout the entire specification.

[0016] An embodiment of the present disclosure will be described with reference to the drawings. An image forming apparatus according to the present embodiment is, for example, an inkjet printer, which forms an image by ejecting ink droplets onto a recording medium such as paper. In the following, an inkjet printer, which is an example of an image forming apparatus, will be described as an example.

[0017] [Configuration of the inkjet printer 100] Fig. 1 is a schematic diagram showing an example of the configuration of an inkjet printer 100 according to this embodiment. Fig. 2 is a block diagram showing the main parts of a control system of the inkjet printer 100. As shown in Figs. 1 and 2, the inkjet printer 100 includes a transport section 10, a supply section 20, a discharge section 30, an ink supply section 40, an image forming section 50, an image reading section 60, an operation display section 70, an input / output interface 80, and a control section 90.

[0018] The transport section 10 has a plurality of members related to transport, such as a transport belt 11, a driving roller 12, and a driven roller 13. The transport section 10 transports the recording medium M by the transport operation of the plurality of members, such as the transport belt 11. Specifically, in the transport section 10, the transport belt 11 is stretched across the driving roller 12 and the driven roller 13, and is driven by driving the driving roller 12 to rotate. As a result, the recording medium M supplied from the supply section 20 is transported to the image forming section 50 while being placed on the transport surface 11a of the transport belt 11, and after an image is formed (printed) in the image forming section 50, it is transported to the discharge section 30.

[0019] The recording medium M may be any of various media capable of fixing ink ejected from an inkjet head 55 (described later). The recording medium M may be, for example, a sheet-like medium such as paper, cloth (woven fabric), or resin. Note that the recording medium M is not limited to a sheet-like medium, and may be a roll-like medium such as paper, cloth, or resin.

[0020] Further, while the conveying unit 10 is illustrated here as an example in which the conveying belt 11 conveys the recording medium M, the conveying unit 10 is not limited to the conveying belt 11 and may be configured to convey the recording medium M by a drum or roller.

[0021] The supply section 20 has a supply stacking section 21 and a supply conveying section 22. The supply stacking section 21 stacks and stores a plurality of recording media M. The supply conveying section 22 conveys and supplies the recording media M from the supply stacking section 21 to the conveying section 10. The supply stacking section 21 is configured to be able to rise and fall, and when the topmost recording medium M is conveyed to the conveying section 10 by the supply conveying section 22, the supply stacking section 21 rises so that the recording medium M that has become the topmost after the conveying can be conveyed to the supply conveying section 22.

[0022] The discharge section 30 has a discharge stacking section 31 and a discharge conveying section 32. The discharge stacking section 31 stacks and stores a plurality of recording media M. The discharge conveying section 32 conveys the recording media M discharged from the conveying section 10 to the discharge stacking section 31. The discharge stacking section 31 is configured to be capable of rising and lowering, and when the recording media M is conveyed from the discharge conveying section 32 to the discharge stacking section 31, the discharge stacking section 31 descends.

[0023] The supply conveying section 22 and the discharge conveying section 32 each have, for example, a plurality of rollers, and convey the recording medium M by rotating the rollers. The supply conveying section 22 and the discharge conveying section 32 are not limited to rollers, and may be configured with a belt, or may be configured with a combination of rollers and belts.

[0024] When a roll-shaped medium is used as the recording medium M, an unwinding roller on which the roll-shaped medium is stored in a wound state is used instead of the supply stacking unit 21. Also, a take-up roller that takes up the roll-shaped medium is used instead of the discharge stacking unit 31. The roll-shaped medium is transported to the transport unit 10 by rotating the unwinding roller, and is taken up by the take-up roller by rotating the take-up roller.

[0025] A post-processing device may be provided between the conveying section 10 and the discharging section 30 to perform post-processing on the recording medium M on which an image is formed by the image forming section 50. One example of the post-processing device is a fixing device that fixes ink to the recording medium M. When, for example, an ultraviolet-curable ink is used as the ink, a fixing device is used that irradiates the recording medium M with ultraviolet rays to fix the ink to the recording medium M. When, for example, an aqueous ink or a solvent ink is used as the ink, a fixing device is used that fixes the ink to the recording medium M by a method such as drying. Furthermore, a device other than a fixing device, such as a cutting device that cuts the recording medium M to a desired length, may be used as the post-processing device.

[0026] The ink supply unit 40 is connected to the image forming unit 50 via a flow path 42, which is an ink supply path, and is a device that supplies ink to a first sub-tank 52a of the image forming unit 50, which will be described later. The ink supply unit 40 has a main tank 41 and components (not shown) related to ink supply (e.g., a pump and a valve, etc.). The main tank 41 stores ink to be supplied to the first sub-tank 52a at room temperature. The ink supply unit 40 supplies ink from the main tank 41 to the first sub-tank 52a via the flow path 42 using a pump (not shown) or the like.

[0027] The image forming unit 50 has a carriage 51, a first sub-tank 52a, a second sub-tank 52b, flow paths 53a, 53b, and 53c, a head driving unit 54, and an inkjet head (hereinafter, simply referred to as a "head") 55, and the like.

[0028] 1, for the sake of simplicity, the ink supply units 40 and image forming units 50 for one color are shown, but the ink supply units 40 and image forming units 50 are arranged according to the number of colors to be used. For example, when four colors, yellow (Y), magenta (M), cyan (C) and black (K), are used, ink supply units 40 and image forming units 50 for four colors are arranged, and the image forming units 50 are arranged so as to be lined up at a predetermined interval along the transport direction T.

[0029] Although not shown, the second sub-tank 52b and the inkjet head 55 are connected in a tree-like configuration to the downstream side of the first sub-tank 52a. However, in FIG. 1, only one of each is shown for the sake of simplicity.

[0030] The carriage 51 is a housing that holds inside the first sub-tank 52a, the second sub-tank 52b, the flow paths 53a, 53b and 53c, the head drive unit 54, the head 55, and devices and members necessary for image formation.

[0031] The first sub-tank 52a is connected to the downstream side of the main tank 41. The first sub-tank 52a stores ink supplied from the main tank 41 in the carriage 51. The ink in the sub-tank 52 is supplied to the second sub-tank 52b via a flow path 53a, which is an ink supply path, by using a pump (not shown) or the like in the carriage 51.

[0032] Although not shown, the second sub-tank 52b is connected in plurality to the downstream side of the first sub-tank 52a. The second sub-tank 52b stores the ink supplied from the first sub-tank 52a in the carriage 51. The ink in the second sub-tank 52b is supplied to a manifold 56 of the head 55, which will be described later, through a flow path 53b, which is an ink supply path, by using a pump (not shown) or the like in the carriage 51. The ink supplied to the manifold 56 is returned to the second sub-tank 52b through a flow path 53c. In other words, the flow paths 53b and 53c form a circulation flow path that circulates the ink between the second sub-tank 52b and the manifold 56.

[0033] Based on the control of a control unit 90 (described later), the head driving unit 54 outputs a driving voltage corresponding to the image data of the image to be formed to a piezoelectric element 58 of a head 55 (described later). The driving voltage from the head driving unit 54 drives the piezoelectric element 58, causing it to eject an amount of ink corresponding to the image data from a nozzle 59 of the head 55 (described later).

[0034] A plurality of heads 55 are connected to the downstream side of each of the plurality of second sub-tanks 52b. In other words, although not shown, a plurality of second sub-tanks 52b and heads 55 are connected in a tree shape to the downstream side of the first sub-tank 52a.

[0035] The head 55 has a manifold 56, pressure chambers 57, piezoelectric elements 58, and nozzles 59. The head 55 has a plurality of nozzles 59, and the pressure chambers 57 and piezoelectric elements 58 are provided in accordance with the number of nozzles 59.

[0036] The manifold 56 communicates with a plurality of pressure chambers 57, and ink supplied to the manifold 56 is supplied to the pressure chambers 57. The pressure chambers 57 are spaces in which the ink to be ejected is stored, and have piezoelectric elements 58 provided on their walls. One end of the nozzle 59 communicates with the pressure chambers 57, and the other end is an open end.

[0037] A driving voltage is applied to the piezoelectric element 58 from the head driving unit 54. When the driving voltage from the head driving unit 54 is applied to the piezoelectric element 58, the piezoelectric element 58 deforms in response to the applied driving voltage, and the pressure chamber 57 deforms. Then, due to the deformation of the pressure chamber 57, the pressure on the ink in the pressure chamber 57 that is supplied to the nozzle 59 changes.

[0038] Therefore, when a drive voltage from the head drive unit 54 is applied to the piezoelectric element 58, the piezoelectric element 58 and the pressure chamber 57 are deformed, causing a pressure change in the ink inside the pressure chamber 57. As a result, the ink inside the pressure chamber 57 is ejected from the nozzle 59. In this manner, droplets of ink are ejected from the nozzle 59, forming an image on the recording medium M being transported.

[0039] In the carriage 51, the heads 55 may be configured to be a single-pass (one-pass) type that forms an image in one scan, or a scan (multi-pass) type that forms an image in multiple scans. In the case of the single-pass type, the carriage 51 has heads 55 arranged in the width direction of the recording medium M (direction perpendicular to the transport direction T of the recording medium M) in the number equal to the image formation width.

[0040] The image reading unit 60 is disposed downstream of the image forming unit 50 in the transport direction T of the recording medium M, and reads an image such as a predetermined pattern image formed on the recording medium M transported by the transport belt 11. The image reading unit 60 outputs the result of reading the predetermined pattern image to the control unit 90. The pattern image is an image used when correcting the landing position of ink in the adjustment process described below. The image reading unit 60 is, for example, a line sensor using a CCD (Charge Coupled Devices) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor.

[0041] Although not shown, the inkjet printer 100 also includes a maintenance unit that performs maintenance such as cleaning of the head 55 .

[0042] The operation display unit 70 is, for example, a flat panel display such as a liquid crystal display or an organic EL (Electro Luminescence) display with a touch panel. The operation display unit 70 displays an operation menu for the user, information related to image data, and various states of the inkjet printer 100. The operation display unit 70 also includes a plurality of keys and accepts various input operations from the user.

[0043] The input / output interface 80 mediates the transmission and reception of data between the external device 200 and the control unit 90. The input / output interface 80 is configured, for example, by any one of various serial interfaces, various parallel interfaces, or a combination of these.

[0044] The external device 200 is, for example, a personal computer or a facsimile machine, and supplies print jobs, image data, and the like to the control unit 90 via an input / output interface 80 .

[0045] The control unit 90 includes a CPU (Central Processing Unit) 91, a RAM (Random Access Memory) 92, a ROM (Read Only Memory) 93, and a storage unit 94.

[0046] The CPU 91 reads out various control programs and setting data stored in the ROM 93, stores them in the RAM 92, and executes the programs to perform various arithmetic processing. For example, the control unit 90 generates a drive signal for an image to be formed based on image data received from the input / output interface 80, and outputs the drive signal to the head 55.

[0047] The RAM 92 provides a working memory space for the CPU 91 and stores temporary data. The RAM 92 may include a non-volatile memory.

[0048] The ROM 93 stores various control programs and setting data executed by the CPU 91. Note that, instead of the ROM 93, a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

[0049] The storage unit 94 stores print jobs and image data related to the print jobs input from the external device 200 via the input / output interface 80. As the storage unit 94, for example, a non-volatile semiconductor memory (so-called flash memory) or an HDD (Hard Disk Drive) is used, and a DRAM (Dynamic Random Access Memory) or the like may also be used in combination.

[0050] The control unit 90 is connected to the transport unit 10, supply unit 20, discharge unit 30, ink supply unit 40, image forming unit 50, image reading unit 60, operation display unit 70, input / output interface 80, etc. The control unit 90 controls the overall operation of the inkjet printer 100. The transport unit 10, supply unit 20, discharge unit 30, ink supply unit 40, image forming unit 50, image reading unit 60, operation display unit 70, input / output interface 80, etc. are controlled by the control unit 90 to execute predetermined processes.

[0051] In this embodiment, the control unit 90 performs an adjustment process to adjust the landing position of the ink ejected from the head 55. The adjustment process will be described in detail later.

[0052] Fig. 3 is a functional block diagram showing an example of the configuration of control unit 90 in Fig. 2. As shown in Fig. 3, control unit 90 has a landing distance measurement unit 95, a determination unit 96, a drive waveform setting unit 97, and a storage unit 94. Note that Fig. 3 shows only functions related to the adjustment process according to this embodiment.

[0053] The landing distance measuring unit 95 measures the landing distance, which is the distance between the ink droplets that form the pattern image read by the image reading unit 60. When measuring the landing distance, the landing distance measuring unit 95 measures the distance between the centers of gravity of the respective ink droplets.

[0054] A determination unit 96 compares the landing distance measured by the landing distance measurement unit 95 with a set range pre-stored in the memory unit 94, and determines whether the landing distance is included within the set range.

[0055] The drive waveform setting unit 97 sets a drive waveform based on the determination result by the determination unit 96. The drive waveform is a waveform of a drive voltage for driving the piezoelectric element 58. The drive waveform setting unit 97 supplies the set drive waveform to the head driving unit 54 of the image forming unit 50.

[0056] The storage unit 94 stores various data used by the control unit 90. For example, the storage unit 94 stores a setting range used by the determination unit 96 in advance.

[0057] [Operation of the inkjet printer 100] The operation of the inkjet printer 100, which is an image forming apparatus according to this embodiment and has the above configuration, will be described.

[0058] In the inkjet printer 100, when an image is formed on a recording medium M, the recording medium M is supplied from the supply unit 20 to the conveying unit 10. The image forming unit 50 ejects ink onto the recording medium M conveyed by the conveying unit 10, and forms an image on the recording medium M.

[0059] At this time, the ink stored in the main tank 41 of the ink supply unit 40 is supplied to the image forming unit 50 via the flow path 42. The ink supplied to the image forming unit 50 is supplied to the head 55 via the first sub-tank 52a, the flow path 53a, the second sub-tank 52b, and the flow paths 53b and 53c. The ink supplied to the head 55 is supplied to the pressure chamber 57 via the manifold 56 and stored therein.

[0060] When a drive voltage is applied to the piezoelectric element 58 forming the wall surface of the pressure chamber 57, the piezoelectric element 58 deforms, thereby deforming the pressure chamber 57. As a result, the ink stored in the pressure chamber 57 is ejected as droplets from the nozzle 59, and an image is formed on the recording medium M.

[0061] Then, the recording medium M on which the image has been formed by the image forming section 50 is conveyed to the discharge section 30 by the conveying section 10.

[0062] (Drive waveform) As described above, when ink droplets are ejected from nozzle 59, a drive voltage having a waveform made up of a plurality of pulses is applied to piezoelectric element 58. In the following description, the waveform of the drive voltage applied to piezoelectric element 58 is referred to as the "drive waveform."

[0063] In the present embodiment, a drive voltage having a first drive waveform 500 or a second drive waveform 600 is applied to the piezoelectric element 58 depending on the state of the image formed on the recording medium M. Also, in pixel regions in the formed image where ink does not land, a drive voltage having a third drive waveform 700 is applied to the piezoelectric element 58 under predetermined conditions.

[0064] (First driving waveform 500) 4 is a schematic diagram for explaining an example of a first driving waveform 500. The first driving waveform 500 is a 1 dpd (drop per dot) driving waveform applied to the piezoelectric element 58 when ejecting a first ink droplet, which is one ink droplet per pixel in an image formed on the recording medium M.

[0065] 4, the first driving waveform 500 includes an expansion pulse 501 and a contraction pulse 502 that is applied consecutively after the expansion pulse 501. In addition, an interval I511 is provided after the contraction pulse 502. The expansion pulse 501 and the contraction pulse 502 constitute a voltage applied to the piezoelectric element 58. The expansion pulse 501, the contraction pulse 502, and the interval I511 form one cycle for ejecting a first ink droplet per pixel of a formed image.

[0066] In this example, the expansion pulse 501 has a voltage of V1 and a pulse width of 1AL. The contraction pulse 502 has a voltage of V2 and a pulse width of 2AL. Here, "AL" is 1 / 2 the acoustic resonance period of the pressure wave in the channel filled with ink. AL is obtained, for example, by measuring the speed of ink droplets ejected from the nozzle 59 when a square wave pulse is applied to the piezoelectric element 58, and determining the pulse width at which the ejection speed of the ink droplets is maximized when the pulse width is changed while the square wave voltage is kept constant.

[0067] (Second driving waveform 600) 5 is a schematic diagram for explaining an example of the second driving waveform 600. The second driving waveform 600 is a 2 dpd driving waveform applied to the piezoelectric element 58 when ejecting the second ink droplets, which are two ink droplets per pixel in an image formed on the recording medium M.

[0068] 5, the second driving waveform 600 is a combination of an expansion pulse 601, a contraction pulse 602, an expansion pulse 603, contraction pulses 604 and 605, an expansion pulse 606, and contraction pulses 607 and 608 in this order. The expansion pulse 611, the contraction pulse 602, the expansion pulse 603, and the contraction pulse 604 are applied consecutively. Also, the expansion pulse 606 and the contraction pulse 607 are applied consecutively.

[0069] An interval I611 is provided between the contraction pulse 604 and the contraction pulse 605. An interval I612 is provided between the contraction pulse 605 and the expansion pulse 606. An interval I613 is provided between the contraction pulse 607 and the contraction pulse 608. An interval I614 is provided after the contraction pulse 608. Each expansion pulse and contraction pulse constitutes an applied voltage to the piezoelectric element 58.

[0070] Expansion pulses 601, 603, and 606, contraction pulses 602, 604, 605, 607, and 608, and intervals I611 to I614 form one cycle for ejecting a second ink droplet per pixel of the formed image.

[0071] In this example, the voltage of all inflation pulses 601, 603 and 606 is V1. The voltage of all deflation pulses 602, 604, 605, 607 and 608 is V2.

[0072] Also, the pulse width of the expansion pulse 601 is 0.8 AL. The pulse width of the contraction pulse 602 is 0.4 AL. The pulse widths of the expansion pulses 603 and 606 and the contraction pulses 605 and 608 are 1 AL. The pulse width of the contraction pulses 604 and 607 is 0.5 AL.

[0073] Here, in the second driving waveform 600, pulses from an expansion pulse 601 to a contraction pulse 605 are applied to the piezoelectric element 58, causing a first ink droplet to be ejected from the nozzle 59. Furthermore, pulses from an expansion pulse 606 to a contraction pulse 608 are applied to the piezoelectric element 58 after an interval I613 has elapsed, causing a second ink droplet to be ejected from the nozzle 59.

[0074] At this time, the speed of the second ink droplet is greater than the speed of the first ink droplet. Therefore, before the first ink droplet lands on the recording medium M, the second ink droplet catches up with the first ink droplet in the air and they become one ink droplet. This forms the second ink droplet. In this way, by applying the second drive waveform, which is 2 dpd drive, to the piezoelectric element 58, the second ink droplet, which has a larger ejection volume than the first ink droplet, lands on the recording medium M.

[0075] (Third driving waveform 700) 6 is a schematic diagram for explaining an example of the third driving waveform 700. The third driving waveform 700 is a non-ejection waveform that does not eject ink droplets from the nozzle 59. In the present embodiment, the third driving waveform 700 is applied to the piezoelectric element 58 at a timing when ink droplets are not ejected when the dot interval between two ink droplets is one pixel or two pixels, for example.

[0076] When the third drive waveform 700 is applied to the piezoelectric element 58, no ink droplets are ejected from the nozzle 59, but the ink in the pressure chamber 57 and the nozzle 59 is vibrated. This prevents the ink in the pressure chamber 57 and the nozzle 59 from drying out, and makes it possible to maintain the state of the ink.

[0077] 6, the third driving waveform 700 is a combination of contraction pulses 701, 702, 703, 704, and 705 in this order. The third driving waveform 700 uses, for example, only the contraction pulses 602, 604, 605, 607, and 608 in the second driving waveform 600.

[0078] Furthermore, an interval I711 is provided between the contraction pulse 701 and the contraction pulse 702. An interval I712 is provided between the contraction pulse 702 and the contraction pulse 703. An interval I713 is provided between the contraction pulse 703 and the contraction pulse 704. An interval I714 is provided between the contraction pulse 704 and the contraction pulse 705. An interval I715 is provided after the contraction pulse 705. Each contraction pulse constitutes a voltage applied to the piezoelectric element 58. The contraction pulses 701 to 705 and the intervals I711 to I715 form one cycle for applying a drive voltage to the piezoelectric element 58 when ink droplets are not ejected.

[0079] The voltage of all the contraction pulses 701 to 705 is V2. The pulse width of the contraction pulse 701 is 0.4 AL. The pulse width of the contraction pulses 702 and 704 is 0.5 AL. The pulse width of the contraction pulses 703 and 705 is 1 AL.

[0080] The shape of the third driving waveform 700 is not limited to this example. For example, the third driving waveform 700 may have a shape having only one contraction pulse, and when changing the pulse width, the pulse width of this one contraction pulse may be changed.

[0081] (Regarding deviation in impact position) Generally, when ink droplets are ejected from an inkjet head, meniscus vibration occurs. The meniscus vibration may affect subsequent ejection, and if the meniscus vibration remains, the ejection of ink from the inkjet head becomes unstable, resulting in deviation in the landing position of the ejected ink.

[0082] The range in which the impact of meniscus vibrations causes the impact of deviations in the impact positions of ink droplets ejected from the nozzles is expanding due to faster image formation and higher image quality. Therefore, when correcting the impact position deviations, it is necessary to measure the impact positions for multiple impact patterns and feed back the results to the ejection waveform according to the impact positions.

[0083] On the other hand, under conditions where there is no influence of meniscus vibration, such as a relatively long ink ejection interval, the drive waveform for the piezoelectric element 58 is determined by design so that ink is ejected appropriately. However, if the state of the head 55 changes due to individual differences, the usage environment, aging, etc., the designed drive waveform will cause differences in the ejection speed of ink with different droplet volumes, making it difficult to eject ink appropriately. Therefore, if an image is formed in this state, the ink landing position may be shifted.

[0084] In other words, even if only the adjustment of the landing position deviation is performed under conditions affected by the meniscus vibration, there are cases in which the landing position cannot be corrected with high accuracy. Therefore, the inkjet printer 100, which is the image forming apparatus according to the present embodiment, performs an adjustment process to adjust the landing position deviation of ink droplets, taking into account both the state of the head 55 and the influence of the meniscus vibration.

[0085] Specifically, as an adjustment process, the inkjet printer 100 performs a first adjustment process that adjusts the landing position deviation of ink droplets according to the state of the head 55 under conditions that are not affected by meniscus vibration. Then, after adjusting the landing position deviation of ink droplets by the first adjustment process, the inkjet printer 100 performs a second adjustment process that adjusts the landing position deviation of ink droplets caused by the influence of meniscus vibration.

[0086] (First adjustment process) 7 is a flow chart showing an example of the flow of the first adjustment process by the inkjet printer 100 according to this embodiment. The first adjustment process is a process for adjusting the landing position deviation of ink droplets that occurs depending on the state of the head 55.

[0087] First, in step S1, the image forming unit 50, under the control of the control unit 90, ejects two ink droplets with different ejection amounts from the nozzles 59 of the head 55 at a predetermined dot interval onto the conveyed recording medium M. As a result, a first pattern image is formed in which the two ink droplets land on the recording medium M at a predetermined dot interval.

[0088] Fig. 8 is a schematic diagram showing an example of a first pattern image used in the first adjustment process. The example in Fig. 8 shows a state in which a first droplet, which is one ink droplet, and a second droplet, which is two ink droplets, land on a recording medium M.

[0089] In the first adjustment process, the image forming unit 50, under the control of the control unit 90, ejects ink droplets from the nozzles 59 of the head 55 so that two ink droplets with different ejection amounts land at a predetermined dot interval on the recording medium M, thereby forming a first pattern image. The interval between the two ink droplets in the first pattern image is an interval that is not affected by meniscus vibration, and is, for example, 3 dots or more.

[0090] Returning to FIG. 7, when the first pattern image is formed on the recording medium M, in step S2, the landing distance measuring unit 95 of the control unit 90 measures the landing distance, which is the distance between two ink droplets in the first pattern image.

[0091] In step S3, the determination unit 96 reads out the first set range from the storage unit 94 and compares the measured landing distance with the read out first set range. The determination unit 96 then determines whether the landing distance is included in the first set range. The first set range is an allowable range for the distance between ink droplets within which the landing positions of the ink droplets are determined to be appropriate. Specifically, the first set range may be, for example, about half a pixel of the resolution of the inkjet printer 100, which is the image forming apparatus.

[0092] If the landing distance is within the first set range (step S3: YES), the determination unit 96 determines that the landing positions of the two ink droplets are appropriate and that there is no need to change the drive waveform, and the series of processes then ends.

[0093] On the other hand, if the landing distance is not within the first set range (step S3: NO), the determination unit 96 determines that the landing positions of the two ink droplets are not appropriate and that the drive waveform needs to be changed. Then, in step S4, the drive waveform setting unit 97 changes the drive waveform for driving the piezoelectric element 58 to adjust the landing positions of the ink droplets. Once the drive waveform has been changed, the process returns to step S1.

[0094] When changing the drive waveform in the first adjustment process, the drive waveform setting section 97 changes the pulse width of the drive waveform. For example, when changing the first drive waveform 500 for 1 dpd driving, the drive waveform setting section 97 changes the pulse width of at least one of the expansion pulse 501 and the contraction pulse 502.

[0095] Furthermore, for example, when changing the second drive waveform of 2dpd driving, the drive waveform setting section 97 changes the pulse width of at least one of the expansion pulses 601, 603, and 606 and the contraction pulses 602, 604, 605, 607, and 608. In this case, the drive waveform setting section 97 may change the width of the interval I611 or I613 in addition to the above pulses.

[0096] Specifically, for example, when changing the pulse width of 2.5 μs per AL from 2.5 μs to 2.45 μs, the drive waveform setting unit 97 changes the pulse width of the expansion pulse 601 from 2 μs to 1.95 μs. When changing the pulse width of the contraction pulse 602, the drive waveform setting unit 97 maintains the pulse width (1 μs). When changing the pulse width of the expansion pulse 603, the drive waveform setting unit 97 changes the pulse width from 2.5 μs to 2.45 μs. When changing the pulse width of the contraction pulse 604, the drive waveform setting unit 97 changes the pulse width from 1.25 μs to 1.2 μs.

[0097] The pulse width is preferably adjusted in units of 0.1 μs or less per 1 AL, and more preferably adjusted in units of 0.05 μs or less per 1 AL.

[0098] However, even if the pulse width per 1 AL is changed in each of the first and second drive waveforms, the drive waveform setting unit 97 changes the width of the interval in each drive waveform so that the time of one cycle of the drive voltage remains constant before and after the change.

[0099] For example, in the first drive waveform, the drive waveform setting unit 97 changes the width of the interval I511 in response to a change in the pulse width so that the time of one cycle in the first drive waveform is constant, and in the second drive waveform, the drive waveform setting unit 97 changes the width of the interval I614 so that the time of one cycle in the second drive waveform is constant.

[0100] In this way, in the first adjustment process, when the landing distance of the two ink droplets is not within the first set range, the pulse width of each of the drive waveforms is appropriately changed. By changing the pulse width of the drive waveform, the timing at which the ink droplets land on the recording medium M and the like change, causing the landing positions of the ink droplets to change. Therefore, in the first adjustment process, it is possible to adjust the deviation in the landing positions of the ink droplets that occurs depending on the state of the head 55.

[0101] (Second Adjustment Process) 9 is a flow chart showing an example of the flow of the second adjustment process by the inkjet printer 100 according to this embodiment. The second adjustment process is a process for adjusting the landing position deviation of ink droplets caused by the influence of meniscus vibration generated by the previous ejection of ink droplets.

[0102] First, in step S11, the image forming unit 50, under the control of the control unit 90, ejects two ink droplets from the nozzle 59 of the head 55 continuously or at a predetermined dot interval onto the conveyed recording medium M. This forms a second pattern image in which two ink droplets land on the recording medium M continuously or at a predetermined dot interval. The second pattern image is an image including a plurality of landing patterns of ink droplets landing on the recording medium M, obtained by combining predetermined ejection conditions for the two ink droplets ejected from the nozzle 59.

[0103] 10 is a schematic diagram for explaining the ejection conditions of the ink droplets in the second adjustment process. As shown in FIG. 10, the ejection conditions of the two ink droplets ejected from the nozzles 59 of the head 55 include three types: "ejection amount," "ejection interval," and "ejection order."

[0104] The discharge amount is the amount of ink droplets discharged from the nozzle 59. The discharge amount is classified into "1 dpd" which indicates one drop of droplets, and "2 dpd" which indicates two drops of droplets.

[0105] The ejection interval is the dot (pixel) interval between the ejection of the first ink droplet and the ejection of the next ink droplet when two ink droplets are ejected from the nozzle 59. The ejection interval is classified into "continuous" where two ink droplets are ejected consecutively, "1 on 1 off" where the ejection interval between the two ink droplets is 1 dot, and "1 on 2 off" where the ejection interval between the two ink droplets is 2 dots. Note that "(X) on (Y) off" refers to an ejection pattern in which X dots of ink droplets are ejected, and then Y dots of ink droplets are not ejected.

[0106] The ejection order is the ejection order when two ink droplets are ejected from the nozzle 59. The ejection order is classified into a "1d leading" order in which an ink droplet with an ejection amount of 1 dpd precedes the other of the two ink droplets, and a "2d leading" order in which an ink droplet with an ejection amount of 1 dpd precedes the other.

[0107] In the second adjustment process, the ejection conditions for the ink droplets classified into three types are combined to eject two ink droplets, thereby forming a second pattern image including a plurality of landing patterns.

[0108] Fig. 11 is a schematic diagram showing an example of the second pattern image used in the second adjustment process. The example in Fig. 11 shows landing patterns obtained by all combinations of the ejection conditions shown in Fig. 10, which are classified according to the ejection amount, ejection interval, and ejection order, when two ink droplets are ejected from the nozzle 59.

[0109] As the ejection conditions, two types of ejection amount, three types of ejection intervals, and two types of ejection orders are set, so that there are a total of 12 landing patterns when two ink droplets are ejected.

[0110] Returning to FIG. 9, when the second pattern image is formed on the recording medium M, in step S12, the landing distance measuring unit 95 measures the landing distances for all landing patterns included in the second pattern image.

[0111] In step S13, the determination unit 96 reads out the second set range from the storage unit 94. The second set range is an allowable range for the distance between ink droplets within which the landing positions of the ink droplets are determined to be appropriate in each landing pattern. Specifically, the second set range may be, for example, about half the pixel of the resolution of the inkjet printer 100, which is the image forming apparatus. As the second set range, a pattern-specific set range corresponding to each landing pattern is set in advance. The determination unit 96 compares the measured landing distance in each landing pattern with the pattern-specific set range corresponding to the landing pattern that is included in the second set range, and determines whether each landing distance is included in the pattern-specific set range.

[0112] If all the landing distances in each landing pattern are included within the corresponding pattern-specific setting range (step S13: YES), the determination unit 96 determines that the landing positions of the ink droplets are appropriate and that it is not necessary to change the drive waveform. Then, the series of processes ends.

[0113] On the other hand, if even one of the landing distances for each landing pattern is not included within the corresponding pattern-specific range (step S13: NO), the process proceeds to step S14.

[0114] In step S14, the determination unit 96 determines whether the number of times the landing distance has been measured is within a predetermined number. If the number of times the landing distance has been measured is within the predetermined number (step S14: YES), the determination unit 96 determines that the landing position of the ink droplets is not appropriate and that the drive waveform needs to be changed. Then, in step S15, the drive waveform setting unit 97 changes the drive waveform based on the landing pattern whose landing distance was determined in step S13 to be outside the corresponding pattern-specific setting range, thereby adjusting the landing position of the ink droplets. Once the drive waveform has been changed, the process returns to step S11.

[0115] On the other hand, if the number of measurements of the landing distance exceeds the predetermined number (step S14: NO), the control unit 90 sets the landing pattern, whose landing distance is determined not to be within the corresponding pattern-specific setting range, as a prohibited pattern in step S16. Then, the series of processes ends. Note that, when it is necessary to eject ink droplets in the landing pattern set as the prohibited pattern, it is preferable to form the image by complementing it with, for example, ejecting ink droplets from the adjacent nozzles 59.

[0116] When changing the drive waveform in the second adjustment process, the drive waveform setting section 97 changes a predetermined pulse width in the drive waveform in accordance with the dot interval between two ink droplets.

[0117] For example, consider a case where the landing distance of a landing pattern in which two successive ink droplets are dropped is not within the set range. When the preceding waveform is the second driving waveform 600 of the 2 dpd driving, the driving waveform setting unit 97 changes the pulse width of the contraction pulse 608, which is the final pulse. Note that, instead of changing the pulse width of the contraction pulse 608, a contraction pulse may be generated multiple times, as long as the pulse width of the contraction pulse 608 after the change is within the width (set time) of the interval I614.

[0118] Furthermore, when the preceding waveform is the first driving waveform 500 of 1 dpd driving, the driving waveform setting unit 97 changes the pulse width of the contraction pulse 502, which is the final pulse. Note that, instead of changing the pulse width of the contraction pulse 502, a contraction pulse may be generated multiple times, as long as the pulse width of the contraction pulse 502 after the change is within the width (set time) of the interval I511.

[0119] When the pulse width is changed, the drive waveform setting unit 97 changes the width of the interval in each drive waveform so that the time of one cycle of the drive waveform does not change, as in the first adjustment process. Specifically, for example, the drive waveform setting unit 97 changes the width of the interval I511 in the first drive waveform 500 or the width of the interval 614 in the second drive waveform 600 so that the time of one cycle of the drive waveform becomes constant.

[0120] Also, consider a case where the landing distance of the landing pattern in which the dot interval between two ink droplets is one or two pixels is not included in the set range. In this case, the drive waveform setting unit 97 sets a third drive waveform 700, which is a non-ejection waveform, between the two ink droplets to be ejected. When adjusting the pulse width of the second drive waveform 600, the pulse width of the contraction pulse 608 may be adjusted.

[0121] In this way, in the second adjustment process, the landing distances of two ink droplets are measured for multiple landing patterns under conditions affected by meniscus vibration. Then, if the landing distance is not included in the second set range, the pulse widths of the drive waveforms are changed. As a result, similar to the first adjustment process, the timing at which the ink droplets land on the recording medium M changes, and the landing positions of the ink droplets change. Therefore, in the second adjustment process, it is possible to adjust the landing position deviation of the ink droplets caused by the influence of the meniscus vibration.

[0122] As described above, the inkjet printer 100, which is an image forming apparatus according to this embodiment, performs a first adjustment process to adjust the landing positions of the ink when two inks with different ejection amounts ejected at an interval of at least a predetermined interval land on the recording medium M. After the first adjustment process, the inkjet printer 100 also performs a second adjustment process to adjust the landing positions of the ink when two inks ejected in a plurality of landing patterns obtained by combining the ejection amounts, ejection intervals, and ejection orders land on the recording medium M.

[0123] In this case, the first adjustment process adjusts the deviation of the ink landing position that occurs depending on the state of the head 55, and the second adjustment process adjusts the deviation of the ink landing position that is caused by the influence of meniscus vibration. Therefore, the landing position of the ejected ink can be accurately corrected, and deterioration in the quality of the formed image can be suppressed.

[0124] <Modification> The adjustment processes including the above-described first adjustment process and second adjustment process are preferably performed on all of the nozzles 59. However, from the standpoint of the amount of data to be acquired and the processing speed, it may be difficult to perform the adjustment processes on all of the nozzles 59.

[0125] In that case, for example, all the nozzles 59 in the head 55 are divided into a plurality of regions, such as by rows, and a representative nozzle is set from the plurality of nozzles 59 included in each region. Then, an adjustment process is performed for the representative nozzle, and the drive waveform may be changed for each region.

[0126] However, even if the landing distance of two ink droplets in each region is within the set range, if there is a difference in the landing distance between the regions, there is a possibility that a difference in density will occur depending on the formed image.

[0127] Therefore, in a modification of this embodiment, the landing distance may be adjusted so that the difference in density between adjacent regions is reduced. In other words, the control unit 90 may change the drive waveform so that the difference in density between adjacent regions is reduced.

[0128] Furthermore, even if there is no significant difference in the landing distance of each nozzle 59 within the same head 55, if there is a difference in the landing distance between heads 55, there is a possibility that a difference in density will occur in the formed image.

[0129] In a modification of the present embodiment, even in such a case, the landing distance may be adjusted so as to reduce the difference in density between adjacent heads 55. In other words, the control unit 90 may change the drive waveform so as to reduce the difference in density between adjacent heads 55.

[0130] Fig. 12 is a flowchart showing an example of the flow of the second adjustment process according to a modified example of the present embodiment. This example shows the second adjustment process in which the drive waveform is changed so as to reduce the difference in density between adjacent regions in the same head 55 or between adjacent heads 55. In Fig. 12, the same reference numerals are used for the processes common to the flowchart shown in Fig. 9, and detailed explanations are omitted.

[0131] First, in step S11, a second pattern image is formed, and in step S12, landing distance measuring unit 95 measures the landing distances for all landing patterns included in the second pattern image.

[0132] In step S13, determination unit 96 compares the measured landing distances in each landing pattern with the pattern-specific set ranges corresponding to each landing pattern, and determines whether or not each landing distance is included within the pattern-specific set range.

[0133] If any of the landing patterns has an impact distance that is not within the corresponding pattern-specific setting range (step S13: NO), the process proceeds to step S23. In step S23, the drive waveform setting unit 97 changes the drive waveform based on the impact pattern whose impact distance is determined in step S13 to be not within the corresponding pattern-specific setting range, and adjusts the impact position of the ink droplets. Once the drive waveform has been changed, the process returns to step S11.

[0134] On the other hand, if all the landing distances in each landing pattern are included in the corresponding pattern-specific setting range (step S13: YES), the determination unit 96 determines that it is not necessary to change the drive waveform, and the process proceeds to step S21.

[0135] In step S21, the landing distance measurement unit 95 calculates the landing distance difference between adjacent regions or adjacent heads 55. The landing distance difference between adjacent regions is the difference between the landing distance measured for nozzles 59 included in a certain region and the landing distance measured for nozzles 59 included in a region adjacent to the said region. Moreover, the landing distance difference between adjacent heads 55 is the difference between the landing distance measured for nozzles 59 of a certain head 55 and the landing distance measured for nozzles 59 of a head 55 adjacent to the said head 55.

[0136] In step S22, the determination unit 96 compares the calculated landing distance difference with a preset third set range, and determines whether the set distance difference is included within the third set range. If the landing distance difference is included within the third set range (step S22: YES), the determination unit 96 determines that no difference in density is recognized between adjacent regions within the same head 55, or between adjacent heads 55. Then, the series of processes ends.

[0137] On the other hand, if the difference in landing distance is not within the third set range (step S22: NO), the determination unit 96 determines that a difference in density occurs between adjacent regions in the same head 55, or between adjacent heads 55. Then, the process proceeds to step S24.

[0138] In step S24, the drive waveform setting unit 97 changes the drive waveform based on the calculated difference in landing distance. After the drive waveform is changed, the process returns to step S11. The method of changing the drive waveform in this case is the same as the second adjustment process described in the present embodiment, but the drive waveform is changed so that the difference in landing distance between adjacent regions or adjacent heads 55 becomes smaller.

[0139] In this way, in the second adjustment process according to the modified example of the present embodiment, the drive waveform is changed according to the difference in landing distance between adjacent regions or heads 55. This adjusts the landing position deviation of ink droplets within the same region or the same head 55, and also adjusts the landing position deviation between adjacent regions or heads 55. This reduces the density difference within the formed image, and suppresses deterioration in the quality of the formed image. [Explanation of symbols]

[0140] 10. Conveyor 20 Supply section 30 Discharge section 40 Ink supply unit 50 Image forming section 55 Inkjet head 57 Pressure Chamber 58 Piezoelectric element 59 Nozzle 60 Image reading unit 70 Operation display section 80 Input / Output Interface 90 Control section 94 Memory section 95 Impact Distance Measurement Unit 96 Judgment section 97 Drive waveform setting section 100 Inkjet Printer 500 First drive waveform 600 Second driving waveform 700 Third driving waveform

Claims

1. An inkjet head that ejects ink droplets onto a recording medium; a control unit that performs an adjustment process including a first adjustment for adjusting a drive waveform of the inkjet head based on landing positions of the ink droplets of a first pattern image formed by landing two of the ink droplets, which are different in amount and are ejected at an interval of a predetermined interval or more, on the recording medium, and a second adjustment that is performed after the first adjustment and adjusts the drive waveform based on landing positions of the ink droplets of a second pattern image formed by landing two of the ink droplets, which are ejected in a plurality of landing patterns obtained by combining a plurality of ejection conditions, on the recording medium; Equipped Image forming device.

2. The inkjet head comprises: a piezoelectric element that deforms when the drive waveform is applied to change the pressure on the ink droplet therein; The control unit is a landing distance measuring unit that measures a landing distance between two of the ink droplets included in the first pattern image during the first adjustment; a determination unit that compares the landing distance with a first set range and determines whether the landing position of the ink droplet is appropriate; a drive waveform setting unit that changes the drive waveform to adjust the landing position when the landing distance is not included in the first setting range; have The image forming apparatus according to claim 1 .

3. The drive waveform setting unit is When the impact distance is not within the first set range, the pulse width of the pulse included in the drive waveform is changed. The image forming apparatus according to claim 2 .

4. The landing distance measurement unit is During the second adjustment, the landing distance between two of the ink droplets in each of the landing patterns included in the second pattern image is measured; The determination unit is comparing the landing distance of each of the landing patterns with a pattern-specific setting range corresponding to each of the landing patterns to determine whether the landing positions of the ink droplets are appropriate; The drive waveform setting unit is When at least one of the landing distances of the plurality of landing patterns is not included in the corresponding pattern-specific setting range, the driving waveform is changed to adjust the landing position. The image forming apparatus according to claim 2 .

5. The ejection conditions are: a discharge interval during which two of the ink droplets are discharged; The drive waveform setting unit is When the ejection intervals in the landing pattern in which the landing distance is not included in the pattern-specific setting range are continuous, a pulse width of a final pulse among a plurality of pulses included in the driving waveform is changed; When the ejection interval in the landing pattern in which the landing distance is not included in the pattern-specific setting range is 1 dot or 2 dot interval, a non-ejection drive waveform is set between the drive waveforms corresponding to two of the ink droplets. The image forming apparatus according to claim 4 .

6. The inkjet head a plurality of nozzles for ejecting the ink droplets; The control unit is The adjustment process is performed for each of the plurality of nozzles. The image forming apparatus according to claim 1 .

7. The inkjet head a plurality of nozzles for ejecting the ink droplets; When the inside of the inkjet head is divided into a plurality of regions, the adjustment process is performed on a representative nozzle selected from the plurality of nozzles in each of the regions. The image forming apparatus according to claim 1 .

8. The inkjet head a plurality of nozzles for ejecting the ink droplets; The landing distance measurement unit is calculating a difference in landing distance between adjacent regions of the inkjet head, the difference being a difference in landing distance between representative nozzles selected from the plurality of nozzles in each of the regions; The determination unit is Comparing the impact distance difference with a third set range; The drive waveform setting unit is When the difference in landing distance is not included in the third set range, the driving waveform is changed. The image forming apparatus according to claim 4 .

9. A plurality of the inkjet heads are provided, The control unit is The adjustment process is performed for each of the inkjet heads. The image forming apparatus according to claim 1 .

10. A plurality of the inkjet heads are provided, The inkjet heads include Each of the nozzles ejects the ink droplets, The adjustment process is performed on a representative nozzle selected from the plurality of nozzles in each of the inkjet heads. The image forming apparatus according to claim 1 .

11. A plurality of the inkjet heads are provided, The inkjet heads include Each of the nozzles ejects the ink droplets, The landing distance measurement unit is calculating a landing distance difference between representative nozzles selected from the plurality of nozzles of each of the inkjet heads adjacent to each other; The determination unit is Comparing the impact distance difference with a third set range; The drive waveform setting unit is When the difference in landing distance is not included in the third set range, the driving waveform is changed. The image forming apparatus according to claim 4 .

12. adjusting a driving waveform of the inkjet head based on a landing position of the ink droplets of a first pattern image formed by landing two ink droplets, the ink droplets having different ejection amounts being ejected from an inkjet head that ejects ink droplets onto a recording medium at an interval of at least a predetermined interval, on the recording medium; After the adjustment, the driving waveform is adjusted based on the landing positions of the ink droplets of a second pattern image formed by landing two of the ink droplets on the recording medium, the ink droplets being ejected in a plurality of landing patterns obtained by combining a plurality of ejection conditions. Adjustment method.

13. A program for causing a computer to execute the adjustment method according to claim 12.

Images