Image inspection apparatus, image inspection method, program, and inkjet recording apparatus

Abstract

To identify a cause of failure of a nozzle of an inkjet recording apparatus.SOLUTION: An inkjet recording apparatus 1 includes a control unit (identifying means) 50 that identifies the cause of the failure of the nozzle of a head unit 24 (image forming unit 20) based on an image obtained by reading the image (diagnosis chart) formed on a recording medium M by an image forming unit (inkjet recording unit) 20.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image inspection apparatus, an image inspection method, a program, and an inkjet recording apparatus.

Background Art

[0002] Conventionally, an inkjet recording apparatus is known that determines the cause of image quality degradation based on two factors: the density difference S between the density of an image recorded on a recording medium and the density of the image that should originally be recorded, and the number of nozzles in which this S value occurs (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the inkjet recording apparatus disclosed in Patent Document 1 above, the cause of image quality degradation is only roughly classified into six determination results, and it is not possible to identify a specific cause such as foreign matter adhesion to the nozzles.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide an image inspection apparatus, an image inspection method, a program, and an inkjet recording apparatus that can identify the cause of a defect in a nozzle of an inkjet recording apparatus.

Means for Solving the Problems

[0006] To solve the above problems, an image inspection apparatus according to the present invention is an image inspection apparatus that inspects an image formed on a recording medium by an inkjet recording unit, Provided is a specifying means for specifying a cause of a defect in a nozzle of the inkjet recording unit based on an image obtained by reading an image formed on the recording medium by the inkjet recording unit.

[0007] Also, in order to solve the above problems, an image inspection method according to the present invention is an image inspection method executed by an image inspection apparatus that inspects an image formed on a recording medium by an inkjet recording unit, including a specifying step of specifying a cause of a defect in a nozzle of the inkjet recording unit based on an image obtained by reading an image formed on the recording medium by the inkjet recording unit. It includes.

[0008] Also, in order to solve the above problems, a program according to the present invention causes a computer of an image inspection apparatus that inspects an image formed on a recording medium by an inkjet recording unit to function as specifying means for specifying a cause of a defect in a nozzle of the inkjet recording unit based on an image obtained by reading an image formed on the recording medium by the inkjet recording unit. to function.

[0009] Also, in order to solve the above problems, an inkjet recording apparatus according to the present invention includes an inkjet recording unit that records a desired image on a recording medium, and an image inspection apparatus that inspects an image formed on the recording medium by the inkjet recording unit, the image inspection apparatus including specifying means for specifying a cause of a defect in a nozzle of the inkjet recording unit based on an image obtained by reading an image formed on the recording medium by the inkjet recording unit. It includes.

Effect of the Invention

[0010] According to the present invention, it is possible to specify a cause of a defect in a nozzle of an inkjet recording apparatus.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the image inspection apparatus, image inspection method, program, and inkjet recording apparatus according to the present invention will be described with reference to the drawings.

[0013] FIG. 1 is a diagram showing a schematic configuration of an inkjet recording apparatus 1 according to an embodiment of the present invention. The inkjet recording apparatus 1 includes a paper feeding unit 10, an image forming unit 20, a paper discharging unit 30, a control unit 50 (control means, computer) (see FIG. 2), and the like. Under the control of the control unit 50, the inkjet recording apparatus 1 conveys a recording medium M stored in the paper feeding unit 10 to the image forming unit 20, and records an image on the recording medium M in the image forming unit 20. The inkjet recording apparatus 1 conveys the recording medium M on which the image is recorded to the paper discharging unit 30. As the recording medium M, in addition to paper such as plain paper and coated paper, various media capable of fixing the ink landed on the surface, such as cloth or sheet-shaped resin, can be used.

[0014] The paper feeding unit 10 includes a paper feed tray 11 for storing a recording medium M, and a medium supply unit 12 for conveying and supplying the recording medium M from the paper feed tray 11 to the image forming unit 20. The medium supply unit 12 includes an annular belt whose inner side is supported by two rollers. The medium supply unit 12 conveys the recording medium M from the paper feed tray 11 to the image forming unit 20 by rotating the rollers with the recording medium M placed on this belt.

[0015] The image forming unit (inkjet recording unit) 20 includes a conveyance unit 21, a delivery unit 22, a heating unit 23, a head unit 24, a fixing unit 25, a reading unit 26, a delivery unit 27, and the like.

[0016] The conveyance unit 21 holds the recording medium M placed on the outer peripheral curved surface 211a (conveyance surface) of the cylindrical conveyance drum 211, and the conveyance drum 211 rotates and moves in a circular path around a rotation axis extending in the width direction perpendicular to the drawing in FIG. 1. Thereby, the recording medium M on the conveyance drum 211 is conveyed in the conveyance direction along a predetermined conveyance path. That is, the conveyance unit 21 relatively moves the head unit 24 and the recording medium M in a predetermined moving direction (the above-mentioned conveyance direction). The conveyance path of the recording medium M by the conveyance drum 211 is a curved path along the outer peripheral curved surface 211a of the conveyance drum 211. The conveyance drum 211 includes a claw portion and an air intake portion (not shown) for holding the recording medium M on its outer peripheral curved surface 211a. The recording medium M is held on the outer peripheral curved surface 211a by having its end pressed by the claw portion and being attracted to the outer peripheral curved surface 211a by the air intake portion. The conveyance unit 21 has a conveyance drum motor (not shown) for rotating the conveyance drum 211, and the conveyance drum 211 rotates by an angle proportional to the rotation amount of the conveyance drum motor.

[0017] The delivery unit 22 delivers the recording medium M conveyed by the medium supply unit 12 of the paper feeding unit 10 to the conveyance unit 21. The delivery unit 22 is provided at a position between the medium supply unit 12 of the paper feeding unit 10 and the conveyance unit 21, holds one end of the recording medium M conveyed from the medium supply unit 12 with the swing arm portion 221 and picks it up, and delivers it to the conveyance unit 21 via the delivery drum 222.

[0018] The heating unit 23 is provided between the arrangement position of the delivery drum 222 and the arrangement position of the head unit 24, and heats the recording medium M so that the temperature of the recording medium M conveyed by the conveying unit 21 becomes a temperature within a predetermined temperature range. The heating unit 23 has, for example, an infrared heater or the like, and energizes the infrared heater based on a control signal supplied from the control unit 50 to cause the infrared heater to generate heat.

[0019] The head unit 24 has a nozzle surface provided with openings of nozzles for discharging ink exposed to the outside, and discharges ink onto the recording medium M from the openings of the nozzles on the nozzle surface facing the outer peripheral curved surface 211a of the conveyance drum 211 at an appropriate timing according to the rotation of the conveyance drum 211 holding the recording medium M, thereby recording an image. The head unit 24 is arranged such that the nozzle surface and the outer peripheral curved surface 211a are separated by a predetermined distance. In the present embodiment, four head units 24 corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (K) are arranged in the order of Y, M, C, K colors at predetermined intervals from the upstream side in the conveyance direction of the recording medium M. The number of head units 24 can be appropriately changed according to the number of colors to be recorded and the like.

[0020] The fixing unit 25 has an ultraviolet irradiation unit arranged across the width in the width direction of the conveyance drum 211, and irradiates ultraviolet rays from the ultraviolet irradiation unit onto the recording medium M placed on the conveyance drum 211. Thereby, the fixing unit 25 cures and fixes the ink discharged onto the recording medium M. The fixing unit 25 is arranged to face the outer peripheral curved surface 211a between the arrangement position of the head unit 24 and the arrangement position of the delivery drum 271 of the delivery unit 27 in the conveyance direction.

[0021] The reading unit 26 is disposed at a position between the fixing position of the ink by the fixing unit 25 and the arrangement position of the delivery drum 271 in the conveyance direction, so as to be able to image the surface of the recording medium M on the conveyance surface of the conveyance drum 211. The reading unit 26 includes an in-line sensor having a plurality of imaging elements arranged in the width direction. The in-line sensor has a plurality of imaging elements arranged in the width direction, each of which outputs a signal corresponding to the intensity of the incident light. As each imaging element, for example, a CCD (Charge Coupled Device) sensor including a photodiode as a photoelectric conversion element can be used. Also, as each imaging element, for example, a CMOS (Complementary Metal Oxide Semiconductor) sensor can be used. The reading unit 26 acquires one-dimensional imaging data composed of imaging pixel data of imaging pixels linearly arranged over the above-described recordable width in the width direction by the in-line sensor, and outputs the data to the control unit 50. The signal output from the in-line sensor is subjected to current-voltage conversion, amplification, noise removal, analog-digital conversion, etc. in an analog front end (not shown), and is output to the control unit 50 as imaging data indicating the luminance value of the read image. By repeatedly acquiring this one-dimensional imaging data in accordance with the conveyance of the recording medium M, it is possible to acquire the entire imaging data of the recording medium M, and to read the recording medium M (and thus the image recorded on the recording medium M).

[0022] The delivery unit 27 includes a belt loop 272 having an annular belt supported inside by two rollers, and a cylindrical delivery drum 271 that delivers the recording medium M from the conveyance unit 21 to the belt loop 272. The delivery unit 27 conveys the recording medium M delivered from the conveyance unit 21 onto the belt loop 272 by the delivery drum 271, and sends it out to the paper discharge unit 30 by the belt loop 272.

[0023] The paper discharge unit 30 has a plate-shaped paper discharge tray 31 on which the recording medium M sent out from the image forming unit 20 by the delivery unit 27 is placed.

[0024] FIG. 2 is a block diagram showing the main functional configuration of the inkjet recording apparatus 1. The inkjet recording apparatus 1 includes a heating unit 23, a head unit 24 having an inkjet head 241 and a recording head driving unit 242, a fixing unit 25, a reading unit 26, a conveyance driving unit 41, and a maintenance unit 42. The inkjet recording apparatus 1 also includes a communication unit 43, a control unit 50, an operation display unit 60, a bus 80, and the like. Hereinafter, the description of the components that have already been described will be omitted.

[0025] The recording head driving unit 242 supplies a driving signal to the piezoelectric body of the inkjet head 241 to deform it in accordance with the image data at an appropriate timing with respect to the ink ejection mechanism of the inkjet head 241, thereby ejecting ink from the nozzles of the inkjet head 241.

[0026] The conveyance driving unit 41 supplies a driving signal to the conveyance drum motor of the conveyance drum 211 based on a control signal supplied from the control unit 50 to rotate the conveyance drum 211 at a predetermined speed and timing. The conveyance driving unit 41 supplies a driving signal to the motors for operating the medium supply unit 12, the delivery unit 22, and the delivery unit 27 based on a control signal supplied from the control unit 50, thereby supplying the recording medium M to the conveyance unit 21 and discharging it from the conveyance unit 21.

[0027] The maintenance unit 42 is used for the maintenance (normal maintenance) of the inkjet head 241 of the head unit 24. The maintenance unit 42 is provided, for example, at a position adjacent to the conveyance drum 211 in the width direction. When performing maintenance, the head unit 24 moves in the width direction from a position facing the outer peripheral curved surface 211a of the conveyance drum 211 to a position facing the maintenance unit 42.

[0028] In the maintenance (regular maintenance) of the inkjet head 241, first, purge maintenance for discharging ink from each nozzle of the inkjet head 241 is performed. The maintenance unit 42 includes an ink receiving unit for receiving the ink discharged in this purge maintenance. The purge maintenance can be performed, for example, by a method (pressure purge) of forcibly discharging the ink by increasing the supply pressure of the ink to the inkjet head 241. Alternatively, similar to normal image formation, the ink may be discharged by supplying a drive signal to the ink ejection mechanism. By the purge maintenance, foreign matters, air bubbles, and ink solidified in the nozzles inside the inkjet head 241 can be discharged to the outside.

[0029] When the purge maintenance is completed, the maintenance unit 42 performs wiping maintenance for wiping the ink ejection surface of the inkjet head 241 with a wiping cloth or the like. The maintenance unit 42 includes the above-mentioned wiping cloth and a moving mechanism for moving the wiping cloth along the ink ejection surface while bringing the wiping cloth into contact with the ink ejection surface. By performing the wiping maintenance, the ink and foreign matters attached to the ink ejection surface can be removed.

[0030] The communication unit 43 is a communication interface that controls communication operations with external devices. As the communication interface, for example, one or more types corresponding to various communication protocols, such as a LAN board or a LAN card, are included. The communication unit 43 acquires image data to be recorded and setting data (job data) related to image recording from an external device based on the control of the control unit 50, and also transmits status information and the like to the external device.

[0031] The control unit 50 includes a CPU 51 (Central Processing Unit), a RAM 52 (Random Access Memory), a ROM 53 (Read Only Memory), and a storage unit 54.

[0032] The CPU 51 reads out the program 531 and setting data stored in the ROM 53, stores them in the RAM 52, and executes the program 531 to perform various arithmetic processes.

[0033] The RAM 52 provides a working memory space for the CPU 51 and stores temporary data. The RAM 52 may include a non-volatile memory.

[0034] The ROM 53 stores the program 531 to be executed by the CPU 51, setting data, etc. Note that a rewritable non-volatile memory such as a flash memory may be used instead of the ROM 53. Also, the program 531 may be stored in the storage unit 54.

[0035] The storage unit 54 stores a print job (image recording instruction) input from an external device via the communication unit 43 and image data of the image to be recorded related to the print job. Also, the storage unit 54 stores defective nozzle count history data 541. The defective nozzle count history data 541 is data regarding the number of defective nozzles counted when the defective nozzle detection process described later is executed. The date on which the count of the number of defective nozzles in the defective nozzle count history data 541 is performed, that is, the execution date of the defective nozzle detection process, is associated with the number of defective nozzles. As the storage unit 54, for example, an HDD (Hard Disk Drive) is used, and a DRAM (Dynamic Random Access Memory) etc. may be used in combination.

[0036] With such a configuration, the control unit 50 comprehensively controls the overall operation of the inkjet recording apparatus 1 when the CPU 51 executes the program 531.

[0037] The operation display unit 60 is a touch panel composed of a display such as a liquid crystal display (LCD) or an organic ELD (Electro Luminescence Display). The operation display unit 60 displays an instruction menu for the user, information regarding the acquired image data, and the like. Further, the operation display unit 60 includes a plurality of keys and serves as an input unit that accepts input of various instructions, characters, numbers, and other data by the user's key operations.

[0038] The bus 80 is a path for transmitting and receiving signals between the control unit 50 and other components.

[0039] Next, the operation of the inkjet recording apparatus 1 will be described. Specifically, with reference to FIG. 3, the operation of identifying the cause of a defect in the nozzles of the inkjet head 241 will be described. The control unit 50 of the inkjet recording apparatus 1 executes a defective nozzle detection process to realize the above operation. Note that the defective nozzle detection process is executed, for example, every operating day of the inkjet recording apparatus 1 before the start of the job on that day.

[0040] FIG. 3 is a flowchart showing the control procedure of the defective nozzle detection process. As shown in FIG. 3, when the defective nozzle detection process is started, first, the control unit 50 of the inkjet recording apparatus 1 causes the head unit 24 to print a diagnostic chart (test image) (not shown) on the recording medium M (step S101). The diagnostic chart is an evaluation image for measuring the amount of deviation in the landing position of the ink ejected from each nozzle of the head unit 24 on the recording medium M.

[0041] Next, the control unit 50 causes the reading unit 26 to read the diagnostic chart printed on the recording medium M in step S101 (step S102).

[0042] Next, the control unit 50 acquires, from the reading unit 26, the image of the diagnostic chart read in step S102, and based on the image, counts the total number of nozzles (number of defective nozzles (indicator)) that have caused a landing position deviation of 0.75 px (pixel) or more (step S103). The counted number of defective nozzles is associated with the date on which the counting was performed and recorded as defective nozzle number history data 541.

[0043] Next, the control unit 50 uses the defective nozzle number history data 541 to derive the increase rate (slope) of the number of defective nozzles (step S104). Specifically, the control unit 50 derives the increase rate (slope) of the number of defective nozzles between the number of defective nozzles (A) on the current day (the first point in time) when the defective nozzle detection process was executed and the number of defective nozzles (B) at a predetermined point in time (the second point in time) before the current day. The derivation of this increase rate is performed according to the following formula. Here, the predetermined point in time is, for example, the execution date of the most recent defective nozzle detection process. When deriving the above increase rate, the number of defective nozzles on the current day and the number of defective nozzles at the predetermined point in time each use, for example, the average (moving average) of the number of defective nozzles over the most recent 10 days. The increase rate derived in step S104 is associated with the counted number of defective nozzles and the date on which the counting was performed and recorded as defective nozzle number history data 541. Note that the moving average is not limited to the average over 10 days, and may be, for example, the average over 3 days, 5 days, etc. Increase rate (number per day) = ((A) - (B)) / (number of days from the predetermined point in time to the current day)…(formula)

[0044] Next, the control unit 50 refers to the defective nozzle number history data 541 and determines whether the increase rate (number per day) of the number of defective nozzles is transitioning between 0.1 (the first threshold) or more and less than 0.9 (the second threshold) (step S105).

[0045] In step S105, if it is determined that the increase rate of the number of defective nozzles does not transition between 0.1 or more and less than 0.9 (step S105; NO), the control unit 50 ends the defective nozzle detection process. If the increase rate of the number of defective nozzles derived in step S104 is 0.9 or more, it may be determined that a disconnection or damage to the nozzle has occurred, and the operation display unit 60 may be caused to display that fact. Here, FIG. 4 is a graph showing an example of the transition of the number of defective nozzles. As shown in FIG. 4, until the number of days elapsed reaches 90 days, the increase rate of the number of defective nozzles transitions at less than 0.1. Therefore, until the number of days elapsed reaches 90 days, in step S105 above, it is determined that the increase rate of the number of defective nozzles does not transition between 0.1 or more and less than 0.9 (step S105; NO). Further, as shown in FIG. 4, between when the number of days elapsed reaches 90 days and when the number of days elapsed reaches 100 days, the increase rate of the number of defective nozzles transitions at 0.9 or more, that is, the number of defective nozzles is increasing suddenly. Therefore, also between when the number of days elapsed reaches 90 days and when the number of days elapsed reaches 100 days, in step S105 above, it is determined that the increase rate of the number of defective nozzles does not transition between 0.1 or more and less than 0.9 (step S105; NO).

[0046] Also, in step S105, if it is determined that the increase rate of the number of defective nozzles transitions between 0.1 or more and less than 0.9, the control unit 50 identifies the cause of the defect in the nozzles of the inkjet head 241 as foreign matter adhesion to the nozzles (step S106). Here, FIG. 5 is a graph showing an example of the transition of the number of defective nozzles. As shown in FIG. 5, between when the number of days elapsed reaches 120 days, the increase rate of the number of defective nozzles transitions between 0.1 or more and less than 0.9. Therefore, between when the number of days elapsed reaches 120 days, in step S105 above, it is determined that the increase rate of the number of defective nozzles transitions between 0.1 or more and less than 0.9 (step S105; YES).

[0047] Next, the control unit 50 determines whether the number of defective nozzles counted in step S103 is 80 or more and less than 100 (step S107).

[0048] In step S107, if it is determined that the number of defective nozzles is 80 or more and less than 100 (step S107; YES), the control unit 50 performs a recommended normal maintenance display on the operation display unit 60 (step S108). Specifically, as shown in FIG. 6, a message MS1 such as "Please perform normal maintenance." is displayed on the operation display unit 60 as the recommended normal maintenance display. Then, the control unit 50 ends the defective nozzle detection process. In step S107, when it is determined that the number of defective nozzles is 80 or more and less than 100, the control unit 50 may cause the maintenance unit 42 to perform maintenance (normal maintenance) on the inkjet head 241.

[0049] Also, in step S107, if it is determined that the number of defective nozzles is not 80 or more and less than 100 (step S107; NO), the control unit 50 determines whether the number of defective nozzles is 100 or more (step S109).

[0050] In step S109, if it is determined that the number of defective nozzles is 100 or more (step S109; YES), the control unit 50 performs a recommended manual maintenance display on the operation display unit 60 (step S110). Specifically, as shown in FIG. 7, a message MS2 such as "*Color / No.* head manual maintenance is required." is displayed on the operation display unit 60 as the recommended manual maintenance display. Here, manual maintenance means that the operator (user) manually wipes the ink ejection surface of the inkjet head 241 using a dedicated web fixing jig. Manual maintenance generally has a stronger cleaning power than normal maintenance. Then, the control unit 50 ends the defective nozzle detection process.

[0051] Also, in step S109, when it is determined that the number of defective nozzles is not 100 or more (step S109; NO), that is, when it is determined that the number of defective nozzles is less than 80, the control unit 50 ends the defective nozzle detection process.

[0052] As described above, the inkjet recording apparatus 1 includes a control unit (identifying means) 50 that identifies the cause of a defect in the nozzles of the head unit 24 (image forming unit 20) based on an image (diagnostic chart) read from the image formed on the recording medium M by the image forming unit 20. Therefore, according to the inkjet recording apparatus 1, since the cause of a defect in the nozzles of the head unit 24 can be identified, it is possible to reduce unnecessary downtime (interruption time) and extend the replacement life of the head (fulfill the original replacement life).

[0053] Further, the control unit 50 of the inkjet recording apparatus 1 derives a predetermined index (number of defective nozzles) based on the image (diagnostic chart) read by the reading unit 26. Further, the control unit 50 identifies the cause of a defect in the nozzles based on the transition of the derived index (number of defective nozzles). Therefore, according to the inkjet recording apparatus 1, since the cause of a defect in the nozzles is identified based on the transition of the index (number of defective nozzles), that is, considering whether the index has changed gradually or suddenly, etc., the cause of a defect in the nozzle can be suitably identified.

[0054] Further, the control unit 50 of the inkjet recording apparatus 1 identifies the cause of a defect in the nozzles based on the transition of the increase rate (slope) of the derived index (number of defective nozzles). Therefore, according to the inkjet recording apparatus 1, since the cause of a defect in the nozzles is identified based on the transition of the increase rate of the index (number of defective nozzles), when the index has changed gradually, the cause of a defect in the nozzle can be identified as foreign matter adhesion to the nozzle. On the other hand, when the index has changed suddenly, the cause of a defect in the nozzle can be identified as a broken wire or a scratch that has occurred on the nozzle.

[0055] In addition, when the increase rate (slope) of the derived index (number of defective nozzles) is 0.1 or more and less than 0.9 which is larger than the said 0.1, the control unit 50 of the inkjet recording apparatus 1 specifies that the cause of the nozzle defect is foreign matter adhesion. That is, when the derived index (number of defective nozzles) changes gradually, since it is specified that the cause of the nozzle defect is foreign matter adhesion, the cause of the defect of the nozzle can be suitably specified.

[0056] In addition, the control unit 50 of the inkjet recording apparatus 1 recommends normal maintenance for automatically cleaning the nozzles of the image forming unit (inkjet recording unit) 20. Specifically, when it is specified that the cause of the nozzle defect is foreign matter adhesion and the value of the index (number of defective nozzles) reaches the first value (80), the control unit 50 recommends normal maintenance. Therefore, according to the inkjet recording apparatus 1, the foreign matter adhering to the nozzles of the head unit 24 can be maintained at an appropriate timing.

[0057] In addition, the control unit 50 of the inkjet recording apparatus 1 recommends manual maintenance for manually cleaning the nozzles of the image forming unit (inkjet recording unit) 20. Specifically, when it is specified that the cause of the nozzle defect is foreign matter adhesion and the value of the index (number of defective nozzles) reaches the second value (100), the control unit 50 recommends manual maintenance. Therefore, according to the inkjet recording apparatus 1, when it is specified that the cause of the nozzle defect is foreign matter adhesion and the value of the index reaches the second value (100), manual maintenance with stronger cleaning power than normal maintenance is recommended. For this reason, the cleaning of the foreign matter adhering to the nozzles can be appropriately performed.

[0058] Note that the description in the above embodiment is an example of the image inspection apparatus, image inspection method, program, and inkjet recording apparatus according to the present invention, and is not limited thereto. For example, in the defective nozzle detection process (see FIG. 3) of the above embodiment, in step S102, the reading unit 26 is made to read the diagnostic chart printed on the recording medium M. However, the reading of the diagnostic chart may be performed by an offline scanner.

[0059] Also, in the defective nozzle detection process (see FIG. 3) of the above embodiment, in step S103, the total number of nozzles with a landing position deviation of 0.75 px (pixels) or more, that is, the number of defective nozzles, is counted as an index. However, the index is not limited to the number of defective nozzles. For example, the landing position deviation amount (total amount), the average value, median, standard deviation, half-width, etc. of the landing position deviation amount distribution may be counted as the above index.

[0060] Also, in the defective nozzle detection process (see FIG. 3) of the above embodiment, in step S104, the increase rate (slope) of the number of defective nozzles is derived based on the number of days (elapsed days) from a predetermined time point to today. However, the target for the reference is not limited to the number of days (elapsed days). For example, the increase rate (slope) of the number of defective nozzles may be derived based on the operation time, printing time, number of printed sheets, etc. of the inkjet recording apparatus 1 from a predetermined time point to today.

[0061] Also, in the above embodiment, the inkjet recording apparatus 1 has been described by taking an industrial inkjet recording apparatus using UV ink as an example. However, it is also applicable to an aqueous inkjet recording apparatus using aqueous inkjet recording ink.

[0062] Also, in the above embodiment, the case where the inkjet recording apparatus 1 incorporates the image inspection apparatus (reading unit 26, control unit 50, etc.) of the present invention has been described. However, the image inspection apparatus may be separate from the inkjet recording apparatus 1.

[0063] Also, regarding the detailed configuration and detailed operation of each component of the inkjet recording apparatus 1 in the above embodiment, it goes without saying that they can be appropriately changed within the scope not departing from the gist of the present invention.

Explanation of Symbols

[0064] 1 Inkjet recording device 10 Paper feeding unit 11 Supply tray 12 Medium supply unit 20 Image forming unit 21 Conveying unit 22 Handover unit 23 Heating unit 24 Head unit 241 Inkjet head 25 Fixing unit 26 Reading unit 27 Delivery unit 30 Paper discharging unit 31 Paper discharge tray 42 Maintenance unit 50 Control unit 51 CPU 52 RAM 53 ROM 54 Storage unit 60 Operation display unit M Recording medium

Claims

1. An image inspection apparatus for inspecting an image formed on a recording medium by an inkjet recording unit, comprising: specific means for identifying a cause of a defect in a nozzle of the inkjet recording unit based on an image obtained by reading the image formed on the recording medium by the inkjet recording unit. An image inspection apparatus.

2. deriving means for deriving a predetermined index based on the read image, wherein the specific means identifies the cause of the defect in the nozzle based on the change in the index derived by the deriving means. The image inspection apparatus according to claim 1.

3. The index is either the number of defective nozzles, the amount of deviation of the landing position, or the median or standard deviation of the distribution of the amount of deviation of the landing position. The image inspection apparatus according to claim 2.

4. The change in the index is the change in the rate of increase of the index between a first time point and a second time point before the first time point. The image inspection apparatus according to claim 2.

5. The rate of increase of the index is a ratio based on any one of the number of days elapsed from the second time point to the first time point, or the operation time, printing time, or number of printed sheets of the inkjet recording unit. The image inspection apparatus according to claim 4.

6. The specific means identifies that the cause of the defect is foreign matter adhesion when the rate of increase of the index changes between a first threshold value and a second threshold value greater than the first threshold value. The image inspection apparatus according to claim 4.

7. recommending means for recommending normal maintenance for automatically cleaning the nozzles of the inkjet recording unit, wherein the recommending means recommends the normal maintenance when the cause of the defect is identified as foreign matter adhesion by the specific means and the value of the index reaches a first value. The image inspection apparatus according to claim 6.

8. The recommending means is capable of recommending manual maintenance for manually cleaning the nozzles of the inkjet recording unit, and recommends the manual maintenance when the cause of the defect is identified as foreign matter adhesion by the specific means and the value of the index reaches a second value greater than the first value. The image inspection apparatus according to claim 7.

9. control means for controlling a normal maintenance unit for automatically cleaning the nozzles of the inkjet recording unit, wherein the control means When the cause of the defect is identified as foreign matter adhesion by the specific means and the value of the index reaches the first value, the normal maintenance unit automatically cleans the nozzles of the inkjet recording unit. The image inspection apparatus according to claim 6.

10. An image inspection method executed by an image inspection apparatus that inspects an image formed on a recording medium by an inkjet recording unit, a specific step of identifying the cause of a defect in the nozzles of the inkjet recording unit based on an image obtained by reading the image formed on the recording medium by the inkjet recording unit, An image inspection method including the above.

11. A computer of an image inspection apparatus that inspects an image formed on a recording medium by an inkjet recording unit, specific means for identifying the cause of a defect in the nozzles of the inkjet recording unit based on an image obtained by reading the image formed on the recording medium by the inkjet recording unit, A program that functions as such.

12. an inkjet recording unit that records a desired image on a recording medium; an image inspection apparatus that inspects an image formed on the recording medium by the inkjet recording unit, an image inspection apparatus including specific means for identifying the cause of a defect in the nozzles of the inkjet recording unit based on an image obtained by reading the image formed on the recording medium by the inkjet recording unit, An inkjet recording apparatus including the above.

Images