Image forming apparatus and adjustment method

Abstract

To provide an image forming apparatus capable of suppressing occurrence of a streak image, and an adjustment method.SOLUTION: The image forming device (1) includes an obtaining processing unit (51) configured to obtain inspection dot image generated by the DFE2, a detection processing unit (52) configured to detect a defective nozzle based on a result of reading a first inspection image formed by the line head and corresponding to the inspection dot image, and a second inspection image corresponding to each of the nozzles, and an adjustment processing unit (53) configured to increase an amount of the ink discharged from the nozzle adjacent to the defective nozzle. DFE2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and an adjustment method. [Background technology]

[0002] Image forming devices such as printers form images on print media such as sheets based on halftone image data (see, for example, Patent Document 1). For example, known image forming devices include a plurality of nozzles arranged along the width direction of the print medium, which is perpendicular to the transport direction, and an ejection unit that ejects ink from each of the nozzles based on the halftone image data. Also known are image forming devices that are communicably connected to an external image generating device such as a DFE (digital front end) that generates the halftone image data.

[0003] In another known image forming device, the ejection unit detects abnormal nozzles that cannot eject ink properly based on the results of reading predetermined images corresponding to the nozzles formed on the print medium. In this type of image forming device, when an abnormal nozzle is detected, the amount of ink ejected by the nozzles adjacent to the abnormal nozzle is increased. This reduces the occurrence of low-density streak images along the transport direction in the image formed by the image forming device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-205637 Summary of the Invention [Problem to be solved by the invention]

[0005] In the image forming apparatus, even if the amount of ink ejected by the nozzle adjacent to the abnormal nozzle is not increased, the low-density streak image may not appear in the image formed by the image forming apparatus, depending on the method of generating the halftone image data. Here, in the case where the low-density streak image does not appear in the image formed by the image forming apparatus even if the amount of ink ejected by the nozzle adjacent to the abnormal nozzle is not increased, if the amount of ink ejected by the nozzle adjacent to the abnormal nozzle is increased, a high-density streak image along the transport direction may appear in the image formed by the image forming apparatus.

[0006] An object of the present invention is to provide an image forming apparatus and an adjustment method that can suppress the occurrence of streak images. [Means for solving the problem]

[0007] According to one aspect of the present invention, an image forming apparatus is communicably connected to an image generating device that generates halftone image data, and includes an ejection unit, an acquisition processing unit, a detection processing unit, and an adjustment processing unit. The ejection unit includes a plurality of nozzles arranged along a width direction perpendicular to a conveyance direction of a print medium, and ejects ink from each of the nozzles based on the halftone image data. The acquisition processing unit acquires test halftone image data generated by the image generating device based on test image data including a color region of the ink color. The detection processing unit detects faulty nozzles among the plurality of nozzles based on the results of reading a first test image corresponding to the test halftone image data formed on the print medium by the ejection unit and a predetermined second test image corresponding to each of the nozzles. The adjustment processing unit increases the amount of ink ejected by the nozzle adjacent to the faulty nozzle detected by the detection processing unit in the width direction.

[0008] An adjustment method according to another aspect of the present invention is executed by an image forming apparatus communicably connected to an image generating device that generates halftone image data, the image forming apparatus including a plurality of nozzles arranged along a width direction perpendicular to the transport direction of a print medium, and an ejection unit that ejects ink from each of the nozzles based on the halftone image data. The adjustment method includes an acquisition step, a detection step, and an adjustment step. In the acquisition step, test halftone image data is acquired by the image generating device based on test image data including a color region of the ink color. In the detection step, a faulty nozzle among the plurality of nozzles is detected based on the results of reading a first test image corresponding to the test halftone image data formed on the print medium by the ejection unit and a predetermined second test image corresponding to each of the nozzles. In the adjustment step, the amount of ink ejected by the nozzle adjacent to the faulty nozzle detected in the detection step in the width direction is increased. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress the occurrence of muscle images. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing the configuration of an image forming system including an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the configuration of the image forming unit of the image forming apparatus according to the embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing an example of test image data used in the image forming apparatus according to the embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing an example of a first test image and a second test image formed by the image forming apparatus according to the embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing an example of a second test image formed by the image forming apparatus according to the embodiment of the present invention. [Figure 6]FIG. 6 is a flowchart showing an example of a defective nozzle detection process executed in the image forming apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of the present invention, and does not limit the technical scope of the present invention.

[0012] [Configuration of image forming system 100] First, with reference to FIG. 1, the configuration of an image forming system 100 including an image forming apparatus 1 according to an embodiment of the present invention will be described.

[0013] As shown in FIG. 1, the image forming system 100 includes an image forming apparatus 1 and a DFE (digital front end) 2.

[0014] In the image forming system 100, the image forming apparatus 1 and the DFE 2 are connected to each other so as to be able to communicate with each other via a communication network such as a LAN (Local Area Network).

[0015] The image forming apparatus 1 is an inkjet printer that forms an image on a print medium such as a sheet. For example, the image forming apparatus 1 is a production printer. For example, the image forming apparatus 1 forms an image on a sheet. The print medium may be cloth, a plastic film, or the like.

[0016] The DFE 2 is an image processing device that generates halftone image data based on document data to be printed. The image forming device 1 forms an image on a sheet based on the halftone image data generated by the DFE 2. The DFE 2 is an example of an image generating device of the present invention.

[0017] Specifically, the DFE2 performs a rasterization process to convert the data format of the original data into a raster format. The DFE2 also performs a screening process to generate the halftone dot image data based on the original data converted into a raster format. For example, the DFE2 performs an AM screening process to change the size of halftone dots according to the gradation value expressed by the halftone dots, or an FM screening process to change the density of halftone dots according to the gradation value expressed by the halftone dots. The content of the screening process performed by the DFE2, i.e., the method for generating the halftone dot image data, differs depending on the type of DFE2.

[0018] In the image forming system 100, the DFE2 connected to the image forming apparatus 1 is switched depending on the type of image included in the document data. Specifically, in the image forming system 100, when the document data is printed, the DFE2 capable of executing the screen processing that is compatible with the type of image included in the document data is connected to the image forming apparatus 1.

[0019] [Configuration of image forming apparatus 1] Next, the configuration of an image forming apparatus 1 according to an embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 2 is a plan view showing the configuration of an image forming unit 12.

[0020] As shown in FIG. 1, the image forming apparatus 1 includes a sheet conveying section 11, an image forming section 12, an image reading section 13, an operation display section 14, a storage section 15, a communication section 16, and a control section 17.

[0021] The sheet conveying unit 11 conveys sheets stored in a paper feed cassette (not shown) to a paper discharge tray (not shown) via an image forming position by the image forming unit 12 and an image reading position by the image reading unit 13. The sheet conveying unit 11 includes a plurality of conveying rollers used to convey the sheets.

[0022] The image forming unit 12 forms an image based on the halftone image data. The image forming unit 12 also forms an image on a sheet conveyed by the sheet conveying unit 11. As shown in FIG. 2, the image forming unit 12 includes line heads 21 to 24 and a head frame 25.

[0023] 2, each of the line heads 21 to 24 is elongated in a width direction D12 (see FIG. 2) perpendicular to a sheet conveyance direction D11 (see FIG. 2) by the sheet conveyance unit 11. Specifically, each of the line heads 21 to 24 has a length in the width direction D12 corresponding to the width of the largest size sheet that can be accommodated in the sheet feed cassette. The line heads 21 to 24 are arranged side by side at equal intervals along the conveyance direction D11.

[0024] The line head 21 ejects black ink toward the sheet being transported by the sheet transport unit 11. The line head 22 ejects cyan ink toward the sheet being transported by the sheet transport unit 11. The line head 23 ejects magenta ink toward the sheet being transported by the sheet transport unit 11. The line head 24 ejects yellow ink toward the sheet being transported by the sheet transport unit 11.

[0025] Except for the fact that the color of ink that is ejected differs, the line heads 22 to 24 have a common configuration with the line head 21. Only the line head 21 will be described below.

[0026] 2, the line head 21 has three recording heads 20. Each of the recording heads 20 is elongated in the width direction D12. The three recording heads 20 are arranged in a staggered pattern along the width direction D12.

[0027] A plurality of nozzles 26 (see FIG. 2) are provided on the surface of each recording head 20 facing the sheet. In each recording head 20, the plurality of nozzles 26 are arranged along the width direction D12. Specifically, in each recording head 20, the plurality of nozzles 26 are arranged along the width direction D12 at a density corresponding to the printing resolution of the image forming apparatus 1. For example, the plurality of nozzles 26 are arranged at equal intervals along the width direction D12. In other words, each recording head 20 has a nozzle row formed by the plurality of nozzles 26 arranged at equal intervals along the width direction D12. Note that each recording head 20 may have a plurality of the nozzle rows.

[0028] All the nozzles 26 included in the line head 21 are arranged along the width direction D12. Specifically, the three recording heads 20 included in the line head 21 are arranged in a staggered pattern along the width direction D12 so that all the nozzles 26 included in the line head 21 are arranged along the width direction D12 at a density corresponding to the printing resolution of the image forming apparatus 1. The line head 21 ejects ink from each of the nozzles 26 based on the halftone dot image data. The line head 21 is an example of an ejection unit of the present invention.

[0029] Each recording head 20 includes a pressure chamber (not shown), a discharge element (not shown), and an individual flow path (not shown) corresponding to each nozzle 26. The pressure chamber communicates with the nozzle 26 and stores ink. The discharge element discharges ink from the nozzle 26 in response to an input of a drive signal. For example, the discharge element is a piezoelectric element. The discharge element discharges ink from the nozzle 26 by changing the pressure in the pressure chamber in response to an input of the drive signal. The individual flow path is an ink flow path provided between the pressure chamber and a common flow path (not shown) common to the multiple nozzles 26. The multiple individual flow paths corresponding to the multiple nozzles 26 are connected to the common flow path. The common flow path is connected to an ink supply unit (not shown) that supplies ink to each of the pressure chambers.

[0030] The head frame 25 supports the line heads 21 to 24. The head frame 25 is supported by the housing of the image forming apparatus 1. The number of line heads provided in the image forming unit 12 may be one or more. Furthermore, the number of recording heads 20 provided in each of the line heads 21 to 24 does not have to be limited to three.

[0031] The image reading unit 13 reads the image formed on the sheet by the image forming unit 12 .

[0032] As shown in FIG. 1, the image reading unit 13 includes a line sensor 31 and an AFE (analog front end) 32.

[0033] The line sensor 31 is disposed downstream of the image forming unit 12 in the conveying direction D11 (see FIG. 2). The line sensor 31 is capable of reading an image of one line along the width direction D12 (see FIG. 2) from a sheet conveyed by the sheet conveying unit 11. For example, the line sensor 31 is a CIS (contact image sensor). The line sensor 31 includes a plurality of imaging elements arranged side by side in the width direction D12. Each of the imaging elements includes a light-emitting unit and a light-receiving unit. The light-emitting unit emits light toward the sheet conveyed by the sheet conveying unit 11. The light-receiving unit is configured to receive light emitted from the light-emitting unit and reflected by the sheet, and outputs an analog electrical signal corresponding to the amount of received light. The line sensor 31 outputs an analog electrical signal corresponding to an image of one line at predetermined intervals in response to a control signal input from the control unit 17.

[0034] The AFE 32 is an electronic circuit that performs predetermined processing on the analog electrical signal output from the line sensor 31. Specifically, the AFE 32 includes a signal conversion unit that converts the analog electrical signal output from the line sensor 31 into a digital electrical signal (image data). The AFE 32 also includes an image processing unit that performs predetermined image processing, such as shading correction, on the image data output from the signal conversion unit. The AFE 32 outputs the image data output from the image processing unit after the image processing has been performed to the control unit 17.

[0035] The operation display unit 14 is a user interface of the image forming apparatus 1. The operation display unit 14 includes a display unit and an operation unit. The display unit displays various information in response to control instructions from the control unit 17. For example, the display unit is a liquid crystal display. The operation unit inputs various information to the control unit 17 in response to user operations. For example, the operation unit includes a touch panel and operation keys.

[0036] The storage unit 15 is a nonvolatile storage device, such as a flash memory.

[0037] The communication unit 16 is a communication interface that executes wired or wireless data communication with an external communication device such as the DFE 2 via the communication network.

[0038] The control unit 17 performs overall control of the image forming apparatus 1. As shown in FIG. 1, the control unit 17 includes a CPU 41, a ROM 42, and a RAM 43. The CPU 41 is a processor that executes various types of arithmetic processing. The ROM 42 is a non-volatile storage device that stores in advance information such as control programs for causing the CPU 41 to execute various types of processing. The RAM 43 is a volatile or non-volatile storage device that is used as a temporary storage memory (work area) for the various types of processing executed by the CPU 41. The CPU 41 executes the various control programs that are stored in advance in the ROM 42. This allows the image forming apparatus 1 to be controlled overall.

[0039] Incidentally, there is known an image forming device that detects an abnormal nozzle that cannot eject ink normally among the nozzles 26 included in the line head 21 based on the results of reading a predetermined image corresponding to each nozzle 26 of the line head 21 formed on a sheet by the line head 21. In this type of image forming device, when an abnormal nozzle is detected, the amount of ink ejected by the nozzle 26 adjacent to the abnormal nozzle is increased. This prevents low-density streak images from appearing along the transport direction D11 in the image formed by the image forming device.

[0040] Here, in the image forming apparatus, even if the amount of ink ejected by the nozzle 26 adjacent to the abnormal nozzle is not increased, a low-density streak image may not appear in the image formed by the image forming apparatus, depending on the method of generating the halftone image data. Here, in the case where a low-density streak image does not appear in the image formed by the image forming apparatus even if the amount of ink ejected by the nozzle 26 adjacent to the abnormal nozzle is not increased, if the amount of ink ejected by the nozzle 26 adjacent to the abnormal nozzle is increased, a high-density streak image along the transport direction D11 may appear in the image formed by the image forming apparatus.

[0041] In contrast, the image forming apparatus 1 according to the embodiment of the present invention can suppress the occurrence of streak images, as will be described below.

[0042] [Functional configuration of control unit 17] Next, the functional configuration of the control unit 17 will be described with reference to Fig. 1 and Fig. 3 to Fig. 5. Fig. 3 is a diagram showing test image data X10. Fig. 4 is a diagram showing a first test image G10 and a plurality of second test images G20 formed on a sheet by the image forming apparatus 1. Fig. 5 is an enlarged view of a portion of the second test image G20.

[0043] As shown in FIG. 1, the control unit 17 includes an acquisition processing unit 51, a detection processing unit 52, and an adjustment processing unit 53.

[0044] Specifically, an operation control program for causing the CPU 41 to function as each of the above-mentioned processing units is stored in advance in the ROM 42 of the control unit 17. The CPU 41 executes the operation control program stored in the ROM 42 to function as each of the above-mentioned processing units.

[0045] The operation control program may be recorded on a computer-readable recording medium such as a CD, DVD, or flash memory, and may be read from the recording medium and installed in a storage device such as memory unit 15. Some or all of the processing units included in control unit 17 may be configured with electronic circuits. The operation control program may also be a program for causing multiple processors to function as the processing units included in control unit 17.

[0046] The acquisition processing unit 51 acquires inspection halftone image data generated by the DFE 2 based on inspection image data X10 (see FIG. 3) including a black color area X11 (see FIG. 3).

[0047] As shown in Fig. 3, the color region X11 is a long strip-shaped region in the main scanning direction D13 (see Fig. 3) corresponding to the width direction D12. For example, the test image data X10 is raster-format image data having only a black color component. The color region X11 is a monochromatic region composed of pixels having a predetermined density.

[0048] The density of the pixels included in the color region X11 (black density) is preset when the image forming apparatus 1 is shipped from the factory. Note that the density of the pixels included in the color region X11 may be set arbitrarily in response to a user's operation on the operation display unit 14. Also, the density of the pixels included in the color region X11 may be set to the same density as the darkest pixel in the color component data corresponding to black among the four color component data corresponding to cyan, magenta, yellow, and black included in the document data to be printed.

[0049] For example, in the image forming apparatus 1, test image data X10 is stored in the storage unit 15 in advance.

[0050] For example, the acquisition processing unit 51 transmits test image data X10 to the DFE2 and requests the DFE2 to transmit the test halftone image data generated based on the test image data X10. The acquisition processing unit 51 then receives the test halftone image data transmitted from the DFE2 in response to the request from the acquisition processing unit 51.

[0051] The detection processing unit 52 detects faulty nozzles included in the multiple nozzles 26 provided in the line head 21 based on the reading results of a first test image G10 (see Figure 4) corresponding to the test halftone image data formed on the sheet by the line head 21 and a second test image G20 (see Figure 4) corresponding to each nozzle 26 included in the line head 21.

[0052] 4, the first test image G10 is a band-shaped image corresponding to the color region X11 of the test image data X10. The first test image G10 is an image formed using black ink. The color density of the first test image G10 is represented by black halftone dots.

[0053] 4, each of the second test images G20 is a band-shaped image extending along the width direction D12. Specifically, each of the second test images G20 is a band-shaped image extending along the width direction D12 that is formed by ejecting ink from each of the nozzles 26 included in the line head 21, excluding the target nozzle that corresponds to the second test image G20, and is an image that is formed by ejecting more ink from the nozzle 26 adjacent to the target nozzle than from the other nozzles 26.

[0054] FIG. 5 shows a portion of the second test image G20 formed by some of the nozzles 26 included in the line head 21, including the target nozzle. A pair of nozzles 26 adjacent to the target nozzle form a pair of first regions G21 (see FIG. 5) included in the second test image G20. A second region G22 (see FIG. 5) included in the second test image G20 is formed by the target nozzle and each of the nozzles 26 different from the pair of nozzles 26 adjacent to the target nozzle. The second region G22 is an area with a lower density of black than the first region G21. A third region G23 (see FIG. 5) is formed between the pair of first regions G21 by not ejecting ink from the target nozzle. The third region G23 is an area of ​​the same color as the color of the sheet.

[0055] By forming the pair of first regions G21, the density of the third region G23 becomes the same level as the density of the second region G22 in the reading result of the second test image G20 by the image reading unit 13. In other words, the pair of first regions G21 serves to correct the density of the third region G23.

[0056] Here, it is assumed that one abnormal nozzle is included in the line head 21. The abnormal nozzle is a nozzle 26 that is unable to eject ink at the opposing position on the sheet. For example, the abnormal nozzle is a nozzle 26 that is unable to eject ink due to clogging or the like.

[0057] When the line head 21 includes one abnormal nozzle, a low-density streak image G31 appears in the first test image G10 and the plurality of second test images G20, as shown in FIG.

[0058] Here, in the second test image G20 corresponding to the abnormal nozzle among the plurality of second test images G20, the density of the third region G23 formed at a position facing the abnormal nozzle on the sheet is corrected by the pair of first regions G21 on both sides of the third region G23. Therefore, in the second test image G20 corresponding to the abnormal nozzle, a streak image G31 does not appear.

[0059] On the other hand, in the second test images G20 corresponding to the nozzles 26 other than the abnormal nozzle, the density of the third region G23 formed on the sheet at a position opposite the abnormal nozzle is not corrected. As a result, a streak image G31 appears in the second test images G20 corresponding to the nozzles 26 other than the abnormal nozzle.

[0060] That is, by counting the number of streak images G31 included in each second test image G20, it is possible to detect the abnormal nozzle.

[0061] Specifically, if the count value of the number of streak images G31 is "0" in all of the second test images G20, it can be determined that there is no abnormal nozzle.

[0062] Furthermore, if the count value of the number of muscle images G31 in any of the second test images G20 is "0", it is possible to determine that the nozzle 26 corresponding to the second test image G20 with the count value "0" is the abnormal nozzle.

[0063] Furthermore, if the count value of the number of muscle images G31 is "1" or more in all second test images G20, it is possible to determine that each nozzle 26 corresponding to a second test image G20 whose count value is lower than that of the other second test images G20 is the abnormal nozzle.

[0064] Here, in the image forming apparatus 1, even if the line head 21 includes the abnormal nozzle, the streak image G31 (see FIG. 4) caused by the abnormal nozzle may not appear in the first test image G10. Specifically, in the image forming apparatus 1, even if the line head 21 includes the abnormal nozzle, the streak image G31 (see FIG. 4) caused by the abnormal nozzle may not appear in the first test image G10, depending on the method for generating the halftone dot image data.

[0065] Therefore, the detection processing unit 52 detects as the faulty nozzle the nozzle 26 that corresponds to the position of the streak image G31 along the conveying direction D11 contained in the first test image G10, which is detected based on the reading result of the first test image G10, among the nozzles 26 that are determined to be the abnormal nozzle based on the reading result of each second test image G20.

[0066] In other words, in the image forming device 1, even if a nozzle 26 is determined to be an abnormal nozzle based on the reading results of each of the second test images G20, if a streak image G31 is not formed at a position corresponding to the nozzle 26 in the first test image G10, the nozzle 26 is not determined to be the faulty nozzle.

[0067] In addition, the detection processing unit 52 may detect a muscle image G31 along the conveying direction D11 contained in the first test image G10 based on the reading result of the first test image G10, and identify the faulty nozzle corresponding to the muscle image G31 based on the reading result of each of the multiple second test images G20, which are narrowed down based on the detection position of the muscle image G31, among the multiple second test images G20.

[0068] Furthermore, each second test image G20 may be a linear image along the transport direction D11 formed by ejecting ink from only the target nozzle corresponding to the second test image G20 among the multiple nozzles 26 included in the line head 21.

[0069] The color of the color region X11 (see FIG. 3) may be cyan, magenta, or yellow. That is, the color region X11 may be a monochromatic region composed of cyan, magenta, or yellow pixels having a predetermined density. In this case, the first test image G10 and the multiple second test images G20 may be formed by any of the line heads 22 to 24. The detection processing unit 52 may detect the defective nozzle from any of the line heads 22 to 24.

[0070] The acquisition processing unit 51 may also acquire the test halftone dot image data corresponding to each of the colors black, cyan, magenta, and yellow. In this case, the detection processing unit 52 may form a first test image G10 and a plurality of second test images G20 for each of the colors black, cyan, magenta, and yellow, and detect the defective nozzles included in the line heads 21 to 24.

[0071] The adjustment processing unit 53 increases the amount of ink ejected by the nozzle 26 adjacent to the defective nozzle detected by the detection processing unit 52 in the width direction D12.

[0072] For example, the adjustment processing unit 53 increases the amount of ink ejected by a pair of nozzles 26 adjacent to the faulty nozzle in the width direction D12. Alternatively, the adjustment processing unit 53 may increase the amount of ink ejected by one of the pair of nozzles 26 adjacent to the faulty nozzle in the width direction D12. This corrects the density of the low-density streak image caused by the faulty nozzle. This makes it possible to make the low-density streak image less visible.

[0073] For example, the adjustment processing unit 53 increases the amount of ink ejected by a pair of nozzles 26 by adjusting the voltage or waveform of the drive signal input to the ejection elements corresponding to each of the pair of nozzles 26 adjacent to the defective nozzle in the width direction D12.

[0074] Below, an example of the procedure of each process executed by the control unit 17 and the storage method of the present invention will be described.

[0075] [Faulty nozzle detection process] 6, an example of the procedure of the faulty nozzle detection process executed by the control unit 17 in the image forming apparatus 1 will be described below. Here, steps S11, S12, etc. represent the numbers of the processing procedures (steps) executed by the control unit 17. The faulty nozzle detection process is executed when an instruction to execute the faulty nozzle detection process is input via the DFE 2 from an external information processing device that inputs a print job for printing the document data to the image forming system 100. The faulty nozzle detection process may also be executed when an instruction to execute the faulty nozzle detection process is input via the operation display unit 14.

[0076] <Step S11> First, in step S11, the control unit 17 acquires the inspection halftone dot image data. The process of step S11 is an example of an acquisition step of the present invention, and is executed by the acquisition processing unit 51 of the control unit 17.

[0077] Specifically, the control unit 17 transmits the test image data X10 to the DFE2, and requests the DFE2 to transmit the test halftone dot image data generated based on the test image data X10. Then, the control unit 17 receives the test halftone dot image data transmitted from the DFE2 in response to the request from the control unit 17.

[0078] <Step S12> In step S12, the control unit 17 uses the line head 21 to form, on the sheet transported by the sheet transport unit 11, a first test image G10 (see Figure 4) corresponding to the test halftone dot image data acquired by the processing of step S11 and a second test image G20 (see Figure 4) corresponding to each nozzle 26 included in the line head 21.

[0079] <Step S13> In step S13, the control unit 17 uses the image reading unit 13 to read the first test image G10 and the plurality of second test images G20 formed on the sheet by the process of step S12.

[0080] <Step S14> In step S14, the control unit 17 detects the defective nozzles included in the plurality of nozzles 26 provided in the line head 21 based on the results of reading the first test image G10 and the plurality of second test images G20 by the processing in step S13. The processing in steps S12 to S14 is an example of a detection step of the present invention, and is executed by the detection processing unit 52 of the control unit 17.

[0081] Specifically, the control unit 17 counts the number of muscle images G31 included in each of the second test images G20 based on the results of reading the multiple second test images G20. Furthermore, the control unit 17 determines, for each nozzle 26 included in the line head 21, whether or not the nozzle 26 is the abnormal nozzle based on the counted number of muscle images G31 in each of the second test images G20. Then, of the nozzles 26 determined to be the abnormal nozzles, the control unit 17 detects, as the faulty nozzles, the nozzles 26 that correspond to the positions of the muscle images G31 included in the first test image G10 detected based on the results of reading the first test image G10.

[0082] In addition, the control unit 17 may detect the muscle image G31 contained in the first test image G10 based on the reading result of the first test image G10, and identify the position of the faulty nozzle corresponding to the muscle image G31 based on the reading result of each of multiple (e.g., five) second test images G20 narrowed down based on the detected position of the muscle image G31 from among the multiple second test images G20.

[0083] <Step S15> In step S15, the control unit 17 increases the amount of ink ejected by the nozzle 26 adjacent to the defective nozzle detected in the process of step S14.

[0084] Specifically, the control unit 17 increases the amount of ink ejected by a pair of nozzles 26 adjacent to the defective nozzle by adjusting the voltage or waveform of the drive signal input to the ejection element corresponding to each of the pair of nozzles 26.

[0085] In this way, in the image forming apparatus 1, the faulty nozzle is detected based on the results of reading the first test image G10 (see FIG. 4) corresponding to the test halftone image data formed on the sheet by the line head 21 and the second test image G20 (see FIG. 4) corresponding to each nozzle 26 included in the line head 21. Then, the amount of ink ejected by the nozzle 26 adjacent to the faulty nozzle is increased. This makes it possible to suppress the occurrence of high-density streak images along the transport direction D11 due to excessive density correction, compared to a configuration in which the abnormal nozzle is detected based on the results of reading the second test image G20 (see FIG. 4) corresponding to each nozzle 26 included in the line head 21 and the amount of ink ejected by the nozzle 26 adjacent to the abnormal nozzle is increased. Therefore, the image forming apparatus 1 can suppress the occurrence of streak images.

[0086] [Notes on the Invention] The following will provide an outline of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0087] <Appendix 1> An image forming apparatus that is communicatively connected to an image generating device that generates halftone image data, the image forming apparatus comprising: a plurality of nozzles arranged along a width direction perpendicular to the transport direction of a printing medium, an ejection unit that ejects ink from each of the nozzles based on the halftone image data; an acquisition processing unit that acquires test halftone image data generated by the image generating device based on test image data including a color area of ​​the ink color; a detection processing unit that detects faulty nozzles included in the plurality of nozzles based on the reading results of a first test image corresponding to the test halftone image data formed on the printing medium by the ejection unit and a predetermined second test image corresponding to each of the nozzles; and an adjustment processing unit that increases the amount of ink ejected by the nozzle adjacent to the faulty nozzle detected by the detection processing unit in the width direction.

[0088] <Appendix 2> The image forming apparatus described in Appendix 1, wherein the detection processing unit detects as the faulty nozzle, among the nozzles determined to be abnormal nozzles that cannot eject the ink normally based on the reading results of each of the second test images, the nozzles corresponding to the position of a streak image along the transport direction included in the first test image detected based on the reading results of the first test image.

[0089] <Appendix 3> The image forming apparatus described in Appendix 1, wherein the detection processing unit detects a streak image along the transport direction included in the first test image based on the reading result of the first test image, and identifies the faulty nozzle corresponding to the streak image based on the reading result of each of the second test images narrowed down based on the detection position of the streak image from the plurality of second test images.

[0090] <Appendix 4> An image forming apparatus as described in any of Appendices 1 to 3, wherein each of the second test images is a band-shaped image along the width direction formed by ejecting the ink from each of the plurality of nozzles excluding the target nozzle corresponding to the second test image, and is an image formed by ejecting more ink from the nozzle adjacent to the target nozzle than from the other nozzles.

[0091] <Appendix 5> An adjustment method performed by an image forming device that is communicatively connected to an image generating device that generates halftone image data, the image forming device including a plurality of nozzles arranged along a width direction perpendicular to the transport direction of a printing medium, and an ejection unit that ejects ink from each of the nozzles based on the halftone image data, the adjustment method including: an acquisition step of acquiring test halftone image data generated by the image generating device based on test image data including a color area of ​​the ink color; a detection step of detecting faulty nozzles included in the plurality of nozzles based on the reading results of a first test image corresponding to the test halftone image data formed on the printing medium by the ejection unit and a predetermined second test image corresponding to each of the nozzles; and an adjustment step of increasing the amount of ink ejected by the nozzle adjacent to the faulty nozzle detected by the detection step in the width direction. [Explanation of symbols]

[0092] 1. Image forming device 2 DFE 11 Sheet transport section 12 Image forming unit 13 Image reading unit 14 Operation display section 15 Storage section 16 Communications Department 17 Control Unit 20 Recording head 21 Line Head 22 Line Head 23 Line Head 24 Line Head 25 Head Frame 26 nozzles 31 Line Sensor 32 AFE 41 CPU 42 ROM 43 RAM 51 Acquisition processing unit 52 Detection processing section 53 Adjustment processing section 100 Image forming system

Claims

1. An image forming apparatus communicably connected to an image generating apparatus that generates halftone image data, an ejection unit including a plurality of nozzles arranged along a width direction perpendicular to a transport direction of the print medium, and ejecting ink from each of the nozzles based on the halftone dot image data; an acquisition processing unit that acquires test halftone dot image data generated by the image generating device based on test image data including a color region of the ink color; a detection processing unit that detects faulty nozzles included in the plurality of nozzles based on the results of reading a first test image corresponding to the test halftone dot image data formed on the printing medium by the ejection unit and a predetermined second test image corresponding to each of the nozzles; an adjustment processing unit that increases the amount of ink ejected by the nozzles adjacent to the defective nozzles detected by the detection processing unit in the width direction; An image forming apparatus comprising:

2. the detection processing unit detects, as the faulty nozzle, the nozzle that corresponds to the position of a streak image along the transport direction included in the first test image detected based on the reading result of the first test image, among the nozzles that are determined to be abnormal nozzles that cannot normally eject the ink based on the reading result of each of the second test images; The image forming apparatus according to claim 1 .

3. the detection processing unit detects a streak image along the transport direction included in the first test image based on a reading result of the first test image, and identifies the faulty nozzle corresponding to the streak image based on a reading result of each of the second test images narrowed down based on the detection position of the streak image from the plurality of second test images. The image forming apparatus according to claim 1 .

4. each of the second test images is a band-shaped image along the width direction formed by ejecting the ink from each of the nozzles among the plurality of nozzles excluding a target nozzle corresponding to the second test image, and is an image formed by ejecting more ink from the nozzle adjacent to the target nozzle than from the other nozzles; 4. The image forming apparatus according to claim 1.

5. An adjustment method executed in an image forming apparatus that is communicably connected to an image generating device that generates halftone dot image data, the image forming apparatus including a plurality of nozzles arranged along a width direction perpendicular to a conveying direction of a print medium, and an ejection unit that ejects ink from each of the nozzles based on the halftone dot image data, an acquisition step of acquiring test halftone dot image data generated by the image generation device based on test image data including a color region of the ink color; a detection step of detecting a defective nozzle included in the plurality of nozzles based on a reading result of a first test image corresponding to the test halftone dot image data formed on the printing medium by the ejection unit and a predetermined second test image corresponding to each of the nozzles; an adjusting step of increasing the amount of ink ejected by the nozzle adjacent to the defective nozzle detected in the width direction by the detecting step; Adjustment methods including:

Images