JP6558116B2 - Ink jet recording apparatus, ink discharge abnormality detection method, and initial deviation detection method - Google Patents

Description

  The present invention relates to an ink jet recording apparatus, an ink ejection abnormality detection method, and an initial deviation detection method.

  2. Description of the Related Art Conventionally, there is an inkjet recording apparatus that records an image or forms a desired pattern by ejecting ink droplets from a plurality of nozzles. By appropriately controlling the ejection timing of ink from each nozzle, a desired image or the like is formed on a medium that is a target of ink ejection.

  In an inkjet recording apparatus, an inkjet head in which a plurality of nozzles are arranged and an operation related to ink ejection is actually performed is not manufactured exactly the same as the design content due to various factors such as the limit of machine accuracy. Deviation (initial deviation) from the nozzles may occur, resulting in variations in the discharge amount and discharge direction between nozzles. In many cases, such initial deviation is so small as not to have a significant effect on the quality of an image to be formed, and is shipped and used within a range that satisfies a predetermined inspection standard.

  On the other hand, when the ink jet recording apparatus is used, the ink is clogged in the nozzle or fixed to the outside of the nozzle opening, so that the amount of ink discharged from the nozzle opening is reduced or the discharge direction is shifted later. In some cases, ejection failure such as On the other hand, conventionally, a detection operation for detecting a nozzle (discharge failure nozzle) in which such a discharge failure has occurred is performed by photographing and analyzing a predetermined inspection image, and the discharge failure nozzle is used for image formation. Instead, a complementary technique that discharges ink from a neighboring nozzle to compensate for the non-discharge of the defective nozzle and a recovery technique that eliminates the defective discharge by cleaning the nozzle and the nozzle opening are used. (For example, Patent Documents 1 and 2).

JP 2007-160748 A JP 2012-133582 A

  However, even if the initial displacement of the nozzle in the ink jet head is detected together with the ejection failure nozzle in the detection operation, it is difficult to recover using the above recovery technique. In particular, a slight initial shift requires accuracy and labor to identify the nozzle in which the initial shift occurs, but does not necessarily lead to an improvement in image quality. Therefore, when initial deviation and ejection failure are handled together, there is a problem that the operation efficiency and cost performance of the ink jet recording apparatus are lowered.

  An object of the present invention is to provide an ink jet recording apparatus, an ink ejection abnormality detection method, and an initial deviation detection method that can suppress a decrease in operation efficiency and cost performance due to an initial deviation of nozzles.

In order to achieve the above object, the present invention described in claim 1
Recording means for arranging a plurality of nozzles and ejecting ink from the openings of the plurality of nozzles, and among the plurality of nozzles, an initial deviation nozzle having an initial deviation in at least one of an ink ejection amount and an ink ejection direction Adjustment information storage means for holding initial deviation information related to the appearance characteristics of
Reading means for reading an image recorded by the recording means;
An ejection abnormality detecting means for detecting the presence or absence of an ink ejection abnormality from a predetermined test image read by the reading means;
With
The discharge abnormality detection means detects discharge abnormality not based on the initial deviation based on the initial deviation information held by the adjustment information storage means ,
The initial deviation information includes area information indicating the appearance range of the initial deviation,
The ejection abnormality detection means is an ink jet recording apparatus, wherein the ejection abnormality detection reference is made different between the appearance range of the initial deviation and the outside of the appearance range of the initial deviation based on the area information .
The invention according to claim 2
A recording unit in which a plurality of nozzles are arranged and each ejects ink from openings of the plurality of nozzles;
Adjustment information storage means for holding initial deviation information relating to the appearance characteristics of an initial deviation nozzle that has produced an initial deviation in at least one of the ink ejection amount and the ink ejection direction among the plurality of nozzles;
Reading means for reading an image recorded by the recording means;
An ejection abnormality detecting means for detecting the presence or absence of an ink ejection abnormality from a predetermined test image read by the reading means;
With
The discharge abnormality detection means detects discharge abnormality not based on the initial deviation based on the initial deviation information held by the adjustment information storage means,
The test image is an image having a predetermined density,
The initial deviation information includes spatial frequency information related to the periodic appearance characteristics of the detected initial deviation nozzle,
The ejection abnormality detecting means determines whether or not there is an ejection abnormality based on density unevenness of correction data obtained by performing processing for suppressing density change of the spatial frequency for the test image data read by the reading means. Do
This is an ink jet recording apparatus.

The invention of claim 3, wherein, in the ink jet recording apparatus according to claim 1, wherein,
The area information includes detection level information by the reading means of the initial deviation,
The discharge abnormality detection means is characterized in that the discharge abnormality detection reference is set such that the initial deviation is not detected as the discharge abnormality based on the detection level information.

The invention of claim 4, wherein, in the ink jet recording apparatus according to claim 1 or 3 Symbol mounting,
The test image is an image having a predetermined density,
The ejection abnormality detecting means is characterized by determining the presence or absence of the ejection abnormality based on density unevenness of the test image.

The invention of claim 5, wherein, in the ink jet recording apparatus according to claim 1 or 3 Symbol mounting,
The test image is an image having a predetermined density,
The initial deviation information includes spatial frequency information related to the periodic appearance characteristics of the detected initial deviation nozzle,
The ejection abnormality detecting means determines whether or not there is an ejection abnormality based on density unevenness of correction data obtained by performing processing for suppressing density change of the spatial frequency for the test image data read by the reading means. It is characterized by

The invention according to claim 6 is the ink jet recording apparatus according to any one of claims 1 to 5,
The image processing apparatus includes a recording control unit that records the test image in response to a recording operation by the recording unit of the output target image related to the acquired image formation command.

The invention according to claim 7 is the ink jet recording apparatus according to any one of claims 1 to 6,
When a discharge abnormality not due to the initial deviation is detected, a defective nozzle specifying image for specifying a defective nozzle causing the discharge abnormality is formed by the recording unit, and the formed defective nozzle specifying image is formed. And a defective nozzle specifying means for specifying the defective nozzle based on data read by the reading means.

The invention according to claim 8 is the ink jet recording apparatus according to claim 7,
Complementing means for adjusting the ink ejection from the identified defective nozzle and the peripheral nozzles of the defective nozzle to form an output target image supplemented with the defective ink ejection of the defective nozzle by the recording means, It is said.

The invention according to claim 9 is the ink jet recording apparatus according to claim 7 or 8,
Recovery means for recovering defective ink ejection of the defective nozzle;
Recovery control means for performing the operation of the recovery means when the detection status of the defective nozzle satisfies a predetermined first condition;
It is characterized by having.

The invention according to claim 10 is the ink jet recording apparatus according to claim 9,
A notification means for performing a notification operation;
The recovery control unit causes the notification unit to perform a predetermined notification operation when the detection state of the defective nozzle after the recovery operation by the recovery unit satisfies a predetermined second condition.

The invention according to claim 11 is the ink jet recording apparatus according to any one of claims 1 to 10,
The recording means includes the width between the recording means and the recording medium in a width direction perpendicular to the relative movement direction of the recording means and the recording medium on which an image is recorded, over an image formable width with respect to the recording medium. It has a line head capable of ejecting ink without performing relative movement in the direction.

The invention according to claim 12 is the inkjet recording apparatus according to any one of claims 1 to 11,
The recording means has a plurality of recording heads.

The invention according to claim 13 is the ink jet recording apparatus according to any one of claims 1 to 12,
The recording means has a predetermined number of ink ejection blocks in which a plurality of nozzle openings are arranged so that a predetermined direction component in a gap between the openings of the plurality of nozzles is a predetermined arrangement interval,
The predetermined number of the ink ejection blocks are relatively arranged as a whole so that the predetermined direction component in the interval between the openings of the nozzles is a predetermined number of the arrangement interval.

The invention according to claim 14 is the ink jet recording apparatus according to claim 13,
The nozzles belonging to different ink ejection blocks are provided in different recording heads.

Further, the invention of claim 15 is
An ink ejection abnormality detection method for an inkjet head comprising a plurality of nozzles arranged and a recording means for ejecting ink from the openings of the plurality of nozzles,
A reading step of reading a predetermined test image recorded by the recording means;
An ejection abnormality detecting step for detecting the presence or absence of an ink ejection abnormality from the predetermined test image read in the reading step;
Including
In the ejection abnormality detection step, the initial deviation is determined based on initial deviation information related to the appearance characteristic of an initial deviation nozzle that has an initial deviation in at least one of the ink ejection amount and the ink ejection direction among the plurality of nozzles. Detects abnormal discharge and
The initial deviation information includes area information indicating the appearance range of the initial deviation,
In the ejection abnormality detection step, based on the area information, the ejection abnormality detection reference is made different between the appearance range of the initial deviation and the outside of the appearance range of the initial deviation .
In addition, the invention according to claim 16
An ink ejection abnormality detection method for an inkjet head comprising a plurality of nozzles arranged and a recording means for ejecting ink from the openings of the plurality of nozzles,
A reading step of reading a predetermined test image recorded by the recording means;
An ejection abnormality detecting step for detecting the presence or absence of an ink ejection abnormality from the predetermined test image read in the reading step;
Including
In the ejection abnormality detection step, the initial deviation is determined based on initial deviation information related to the appearance characteristic of an initial deviation nozzle that has an initial deviation in at least one of the ink ejection amount and the ink ejection direction among the plurality of nozzles. Detects abnormal discharge and
The test image is an image having a predetermined density,
The initial deviation information includes spatial frequency information related to the periodic appearance characteristics of the detected initial deviation nozzle,
In the ejection abnormality detection step, the presence / absence of the ejection abnormality is determined based on density unevenness of correction data obtained by performing processing for suppressing density change of the spatial frequency on the data of the test image read in the reading step. Do
It is characterized by that.

The invention according to claim 17
An initial deviation detection method for detecting an initial deviation related to ink ejection of each nozzle in a recording unit in which a plurality of nozzles are arranged and ejects ink from openings of the plurality of nozzles,
A detection image recording step of recording a halftone image of a predetermined density as a detection image by the plurality of nozzles;
An image reading step for reading a density distribution of the detection image recorded in the detection image recording step;
A frequency detection step for detecting a frequency component related to a spatial distribution of light and shade of the detection image read in the image reading step;
An initial deviation information identifying step for identifying initial deviation information relating to the appearance characteristics of the density distribution of the frequency satisfying the predetermined appearance criterion detected in the frequency detection step;
It is characterized by including.

The invention described in claim 18 is the initial deviation detecting method according to claim 17 ,
The initial deviation information specified in the initial deviation information specifying step includes area information indicating an appearance range of the detected initial deviation.

The invention according to claim 19 is the initial deviation detecting method according to claim 18 ,
In the initial deviation information specifying step, the gray level distribution obtained in the image reading step is compared with a correction distribution obtained by removing frequency components related to the gray level distribution satisfying the predetermined appearance criterion from the gray level distribution. A range that does not match within the difference condition is specified as the appearance range of the initial deviation.

The invention according to claim 20 is the initial deviation detecting method according to claim 19 ,
In the frequency detection step, a frequency indicating a spectral intensity equal to or higher than a predetermined reference value is detected in a spectral distribution obtained by Fourier transforming the gray distribution,
In the initial deviation information specifying step, the correction distribution is obtained by performing inverse Fourier transform while masking the spectrum of the detected frequency in the spectrum distribution.

The invention according to claim 21 is the initial deviation detection method according to any one of claims 17 to 20 ,
In the frequency detection step, a spatial frequency related to the structure of the recording means and a frequency corresponding to the spatial frequency related to the manufacture of the recording means are specified in advance as characteristic frequencies that can occur in the gray distribution,
In the initial deviation information specifying step, the initial deviation information is specified when the gray level distribution at the characteristic frequency satisfies the predetermined appearance criterion.

The invention according to claim 22 is the initial deviation detection method according to claim 21 ,
The recording means has ink ejection blocks at a plurality of different positions in a predetermined transport direction of a recording medium for recording an image;
The plurality of ink ejection blocks each have a plurality of nozzle openings, each having a narrower arrangement interval in the width direction perpendicular to the transport direction than the arrangement interval of the nozzle openings in each of the ink ejection blocks. Are arranged so that
The characteristic frequency includes an arrangement interval of the nozzle openings of each of the ink ejection blocks.

  According to the present invention, there is an effect that it is possible to suppress a decrease in operation efficiency and cost performance due to the initial displacement of the nozzle.

It is the schematic diagram which looked at the structure of the inkjet recording device of embodiment of this invention from the side. It is a bottom view which shows the nozzle surface of an inkjet head. It is a figure explaining the arrangement | sequence of the nozzle opening part in a nozzle surface. It is a block diagram which shows the function structure of an inkjet recording device. It is a block diagram which shows the function structure of an inspection apparatus. It is a flowchart which shows the control procedure of the initial deviation detection process performed with the test | inspection apparatus of this embodiment. It is a flowchart which shows the control procedure of the initial deviation nozzle detection process called by the initial deviation detection process. It is a figure which shows the example of the test | inspection data in a test | inspection apparatus. It is a figure which shows the example of the defect presence / absence detection image which detects the presence or absence of a discharge defect, and the example of the defect nozzle specific image for identifying a discharge defect nozzle when it detects that there exists a discharge defect. 6 is a flowchart illustrating a control procedure of ejection failure detection processing executed in the inkjet recording apparatus. It is a flowchart which shows the control procedure of the other example of a discharge failure detection process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view of the configuration of an ink jet recording apparatus 100 according to an embodiment of the present invention as viewed from the side.

  The ink jet recording apparatus 100 includes a medium supply unit 10, an image forming unit 20, a medium discharge unit 30, and a control unit 40 (see FIG. 4) (ejection abnormality detection unit, recording control unit, defective nozzle identification unit, complement unit, Recovery control means). In the ink jet recording apparatus 100, the recording medium P (sheet-like medium) stored in the medium supply unit 10 is transported to the image forming unit 20 based on the control by the control unit 40, and after the image is formed, the medium discharge unit 30 is discharged.

The medium supply unit 10 includes a paper feed tray 11 and a transport unit 12.
The paper feed tray 11 is a plate-like member provided so that one or a plurality of recording media P can be placed thereon. The paper feed tray 11 moves up and down according to the amount of the recording medium P placed thereon, and the uppermost one of the recording media P is held at the transport start position by the transport unit 12.
As the recording medium P, in addition to printing paper of various thicknesses, various media such as cells, films, and fabrics that can be supported while being curved on the outer peripheral surface of the image forming drum 21 are used.
The conveying unit 12 includes a plurality of (for example, two) rollers 121 and 122, an annular belt 123 supported by the rollers 121 and 122 on the inner surface, and a recording medium P placed on the paper feed tray 11. A supply unit (not shown) for transferring the uppermost one to the belt 123. The conveyance unit 12 conveys the recording medium P transferred on the belt 123 by the supply unit according to the circular movement of the belt 123 by the rotation of the rollers 121 and 122 and sends the recording medium P to the image forming unit 20.

  The image forming unit 20 includes an image forming drum 21, a delivery unit 22, a head unit 23 (recording unit), an irradiation unit 24, a reading unit 25 (reading unit), a delivery unit 26, and the like.

  The image forming drum 21 has a cylindrical outer peripheral shape, carries the recording medium P on the outer peripheral surface, and a transport path (conveying direction, relative movement direction between the recording means and the recording medium) according to the rotation operation. ) To transport the recording medium P.

  The delivery unit 22 delivers the recording medium P delivered from the transport unit 12 to the image forming drum 21. The delivery unit 22 is provided at a position between the conveyance unit 12 of the medium supply unit 10 and the image forming drum 21. The delivery unit 22 includes a claw part 221 that grips one end of the recording medium P sent by the transport unit 12, a cylindrical delivery drum 222 that guides the recording medium P gripped by the claw part 221, and the like. When the recording medium P acquired from the conveyance unit 12 by the claw unit 221 is sent to the transfer drum 222, the recording medium P moves along the outer peripheral surface of the rotating transfer drum 222 and is guided to the outer peripheral surface of the image forming drum 21 as it is. Passed.

The head unit 23 drops ink droplets at various locations on the recording medium P from a plurality of nozzle openings provided on the nozzle surface facing the recording medium P in accordance with the rotation of the image forming drum 21 on which the recording medium P is carried. An image is formed by discharging the ink. In the ink jet recording apparatus 100 of the present embodiment, four head units 23 are spaced apart from the outer peripheral surface of the image forming drum 21 by a preset distance and are arranged at predetermined intervals. The four head units 23 respectively output CMYK four color inks. As these inks, thermosoftening inks that soften at a predetermined temperature (for example, 60 ° C.) or higher are used. Such an ink is not particularly limited, but a known gel-like ink that is solated by being heated to a predetermined temperature or higher, for example, various inks described in International Publication No. 2012/147760 is used. Is done. The head unit 23 is provided with a heater 235 (see FIG. 4) for heating the ink and maintaining the sol state.
Here, each of the head units 23 forms an image by a single pass method without being moved in the width direction (predetermined direction) which is the rotation axis direction of the image forming drum 21 (direction perpendicular to the conveyance direction of the recording medium P). A line head capable of forming an image over the image formable width on the recording medium P by a combination with the rotation of the drum 21 is provided.

  The irradiation unit 24 irradiates energy rays of a predetermined wavelength, here ultraviolet rays, and cures the ink ejected from the head unit 23 onto the recording medium P. The irradiation unit 24 includes, for example, a light emitting diode (LED) that emits ultraviolet rays, and emits light by applying a voltage to the LEDs and flowing current to irradiate the ultraviolet rays. The irradiation unit 24 is in the vicinity of the outer peripheral surface of the image forming drum 21, and after the ink is discharged from the head unit 23 onto the recording medium P conveyed by the rotation of the image forming drum 21, the surface of the recording medium P Is read on the recording medium P before being read by the reading unit 25.

  In addition, the structure which emits an ultraviolet-ray in the irradiation part 24 is not restricted to LED. The irradiation unit 24 may include, for example, a mercury lamp. In addition, when the ink has a property of being cured by receiving energy rays other than ultraviolet rays, a known light source that emits energy rays having a wavelength for curing the ink is provided instead of the above-described configuration that emits ultraviolet rays.

  The reading unit 25 reads the image of the surface of the recording medium P on which the ink has been ejected. The reading unit 25 includes a line sensor that can capture images over a range in which the head unit 23 can eject ink in the width direction and land on the recording medium P. As each image sensor of the line sensor, a CCD (Charge Coupled Device) sensor, a CMOS sensor, or the like is used. By sequentially imaging the surface of the recording medium P conveyed by the image forming drum 21, two-dimensional imaging data of the recording medium P is obtained. Alternatively, the reading unit 25 may have a sensor capable of performing two-dimensional imaging at a time, or may be configured to image the entire surface of the recording medium P by moving the sensor in the width direction or the like.

  The reading unit 25 is configured to be able to read images of four colors of CMYK ink ejected by the head unit 23, for example, to read an image in each of RGB colors and / or a specific wavelength band. Note that the reading resolution by the reading unit 25 does not necessarily need to be an accuracy that can be disassembled more finely than the ink discharge interval (pitch) from each nozzle of the head unit 23.

  The delivery unit 26 conveys the recording medium P on which ink has been ejected and cured from the image forming drum 21 to the medium discharge unit 30. The delivery unit 26 includes a plurality of (for example, two) rollers 261 and 262, an annular belt 263 supported on the inner surfaces by the rollers 261 and 262, and a cylindrical delivery roller 264. The delivery unit 26 guides the recording medium P on the image forming drum 21 onto the belt 263 by the delivery roller 264, and moves the delivered recording medium P together with the belt 263 that moves around as the rollers 261 and 262 rotate. Then, it is conveyed and sent to the medium discharge unit 30.

  The medium discharge unit 30 stores the recording medium P after image formation sent out from the image forming unit 20 until it is taken out by the user. The medium discharge unit 30 includes a plate-shaped discharge tray 31 on which the recording medium P conveyed by the delivery unit 26 is placed.

  The controller 40 controls the overall operation of the inkjet recording apparatus 100. The functional operation of the control unit 40 will be described in detail later.

FIG. 2 is a bottom view showing the ink ejection surface of the head unit 23.
In the head unit 23, two recording heads 231 and 232 are paired, and a plurality of the pairs are arranged in a staggered manner, so that ink can be ejected across the width of the recording medium P in the width direction. Yes. The plurality of recording heads 231 and 232 are each provided with a plurality of nozzle openings at three different locations in the transport direction.
Here, the group of recording heads 231 and the group of recording heads 232 disposed at the same position in the transport direction are referred to as recording head groups 231T and 232T (ink ejection unit lock), respectively.

FIG. 3 is a diagram illustrating the arrangement of the nozzle openings on the ink ejection surface.
As shown in FIG. 3A, the recording head 231 is provided with nozzle openings on the straight lines 231a, 231b, and 231c extending in the width direction at intervals of 6d, and the positions of the nozzle openings on the straight lines. Are shifted by 2d (predetermined arrangement interval) from each other in the width direction. Further, the recording head 232 is provided with nozzle openings on the straight lines 232a, 232b, and 232c extending in the width direction at intervals of 6d, and the positions of the nozzle openings on each straight line are 2d in the width direction. It's off. Further, the nozzle openings on the recording head 231 and the nozzle openings on the recording head 232 are arranged at a distance d so that the positions in the width direction are staggered, and the nozzle openings as a whole. Are provided at intervals d in the width direction.

When ink ejected from the nozzle openings lands on the recording medium P, the ink spreads and is fixed in a range wider than the interval d (pitch) between the nozzle openings. Therefore, normally, ink can be landed without any break in the width direction by ejecting ink from each nozzle.
On the other hand, as shown in FIG. 3B, if ink is not ejected from any of the nozzle openings, ink is not ejected to the portion, and a gap v11 is generated. Further, when the ink ejection direction from any of the nozzle openings is inclined in the width direction with respect to the normal direction, the ink landing position is also shifted, and gaps v21, v22, and v23 are generated. The widths of the gaps v11, v21 to v23 are determined according to the above-described ink fixing range. Further, when the amount of ink discharged from the nozzle opening is lower than usual, the density of the portion is reduced.

FIG. 4 is a block diagram illustrating a functional configuration of the inkjet recording apparatus 100 according to the present embodiment.
In addition to the image forming unit 20 and the control unit 40 described above, the inkjet recording apparatus 100 includes a transport drive unit 51, a communication unit 61, an operation display unit 62, a notification unit 64 (notification unit), a bus 69, and the like. Prepare.

The image forming unit 20 includes a head driving unit 531 that performs an operation related to ink ejection in the above-described recording heads 231 and 232 (two (predetermined number of recording head groups 231T and 232T)), and a heater 235 that is related to ink heating. A heater driving unit 535 that operates the irradiation unit 24, an irradiation driving unit 54 that operates the irradiation unit 24, a reading driving unit 55 that operates the reading unit 25, a cleaning unit 27 (recovery means), a cleaning driving unit 57, and the like.
Each component of the image forming unit 20 is provided for each of CMYK four colors.

  The head driving unit 531 applies an operation load for ejecting ink from each nozzle opening in accordance with an ink ejection command related to output image data or maintenance of each nozzle, for example, a driving voltage to a piezoelectric element or an electrothermal resistance element. Outputs the applied signal.

As described above, the heater driving unit 535 operates the heater 235 for heating and maintaining the ink at a predetermined temperature. The heater driving unit 535 can turn on and off the heat generation of the heater 235 based on the temperature of ink measured by a temperature sensor (not shown) or the wall surface temperature of an ink chamber in which ink is stored.
The head driving unit 531 and the recording heads 231 and 232 (recording head groups 231T and 232T), the heater driving unit 535, and the heater 235 are included in the head unit 23.

The cleaning unit 27 performs a cleaning operation on the nozzle surface of the head unit 23. The cleaning unit 27 includes, for example, a wiping member for wiping the nozzle surface, a blade member for scraping the ink fixed to the nozzle surface, and the like, and is normally arranged in parallel with the head unit 23 in the width direction. It waits, is moved as necessary, and is brought into contact with the nozzle surface.
The cleaning drive unit 57 operates the cleaning unit 27 under the control of the control unit 40.

  The communication unit 61 is an interface for transmitting and receiving data to and from external electronic devices such as a printer server and various terminal devices such as a personal computer (PC) using a predetermined communication protocol. ). The connection method may be wired or wireless communication via a LAN (Local Area Network), or the communication unit 61 is a connection terminal for direct connection with an external device such as USB (Universal Serial Bus). And a driver may be provided.

  The operation display unit 62 displays various menus, statuses, and the like on the display screen based on the control operation of the control unit 40, receives an input operation by the user, and outputs an operation signal to the control unit 40. For example, a liquid crystal display is used as the display screen, but the display screen is not limited thereto. Further, the display screen can be used as a touch panel by providing a touch sensor over the display screen. In addition, the operation display unit 62 may include an LED lamp indicating a power supply state, a push button switch for switching on / off of the main power source, or performing a reset operation.

  The notification unit 63 performs a predetermined notification operation for the user of the inkjet recording apparatus 100. The notification operation includes, for example, an operation of generating a beep sound or lighting or blinking a lamp, and includes a piezoelectric element that generates a beep sound or a light emitting diode (LED) that lights or blinks.

The control unit 40 includes a CPU 41 (Central Processing Unit), a RAM 42 (Random Access Memory), a storage unit 43 (adjustment information storage means), and the like.
The CPU 41 performs various arithmetic processes related to the operation of the inkjet recording apparatus 100. The RAM 42 provides a working memory space to the CPU 41 and stores temporary data.

The storage unit 43 stores and holds a control program related to the control operation by the CPU 41, and the control program is read and executed by the CPU 41 as necessary. Further, the storage unit 43 converts the image data to be output acquired from the outside via the communication unit 61 and the format used for image formation in the inkjet recording apparatus 100 of the present embodiment by processing the image data. The stored data (raster data) is temporarily stored. The image data to be output is output to the head driving unit 531 at an appropriate timing, and determines whether ink is ejected from each nozzle. The data stored in the storage unit 43 includes various setting data used when generating raster data, for example, an ejection failure nozzle list 431 that identifies ejection failure nozzles that have caused ejection failure, and ink ejection positions. Initial displacement nozzle area information 432 (initial displacement) indicating the presence area (area indicating the appearance range) of the initially displaced nozzles that have been displaced from the beginning, that is, at the time of manufacture of the head unit 23, such as when the head unit 23 is manufactured. Information). Further, the initial deviation nozzle area information 432 can include information on the detection level of the initial deviation nozzle in the area where the initial deviation nozzle exists. In this case, adjustment is appropriately made so that there is no deviation between a detection level in the inspection apparatus 200 described later and a detection level by the reading unit 25 of the inkjet recording apparatus 100.
As the storage unit 43, a combination of a DRAM (Dynamic Random Access Memory) capable of reading and writing at a high speed at a high speed, for example, and a nonvolatile memory capable of holding data even when the power is turned off is preferably used. It is done. Further, a control program and initial setting data for the entire operation of the inkjet recording apparatus 100 may be stored in a mask ROM.

  The transport driving unit 51 performs an operation of sending the recording medium P from the medium supply unit 10 to the image forming unit 20 and further moving the recording medium P to the medium discharge unit 30 based on the control of the control unit 40. The conveyance drive unit 51 sends the paper from the paper feed tray 11 to the conveyance unit 12 at an appropriate timing, operates the claw unit 221 while rotating the image forming drum 21 at an appropriate speed by a rotation motor or the like, and delivers the transfer unit 12 from the conveyance unit 12 By placing the recording medium P on the outer peripheral surface of the image forming drum 21 via 22, the recording medium P is conveyed while facing the nozzle surface of the head unit 23. Then, the conveyance driving unit 51 separates the recording medium P from the outer peripheral surface of the image forming drum 21 at an appropriate timing, and sends the recording medium P to the paper discharge tray 31 via the delivery unit 26.

  These units are connected to each other via a bus 69 so that data can be exchanged.

Next, the inspection apparatus 200 that detects the initial deviation of ink ejection at each nozzle of the head unit 23 of the present embodiment will be described.
FIG. 5 is a block diagram illustrating a functional configuration of the inspection apparatus 200.

  The inspection apparatus 200 includes a control unit 2040, an output image generation unit 2045, an image processing unit 2046, a conveyance driving unit 2051, a reading driving unit 2055, a reading unit 2025, an irradiation driving unit 2054, and an irradiation unit 2024. And a communication unit 2061, an operation display unit 2062, and the like, and the head unit 23 used in the above-described inkjet recording apparatus 100 is attached for inspection.

  The transport driving unit 2051 moves the inspection recording medium at a predetermined speed while facing the nozzle surface of the head unit 23 and the imaging surface (reading surface) of the reading unit 2025.

The irradiation unit 2024 has the same configuration as the irradiation unit 24 and irradiates the inspection recording medium with energy rays (ultraviolet rays) that fix the ink ejected from the recording heads 231 and 232 to the inspection recording medium.
The irradiation drive unit 2054 operates the irradiation unit 2024 based on a control signal from the control unit 2040.

The reading unit 2025 is a line sensor similar to the reading unit 25, and the resolution and the like may be the same as or different from those of the reading unit 25.
The reading drive unit 2055 causes the reading operation by the reading unit 2025 to be performed at an appropriate timing.

  The communication unit 2061 is an interface for performing communication between the inspection apparatus 200 and an external device. Like the communication unit 61, the communication unit 2061 is, for example, a NIC.

  The operation display unit 2062 displays an operation menu and status information shown to the user of the inspection apparatus 200, receives an input operation of the user, and outputs it to the control unit 2040 as an operation signal. The specific configuration of the operation display unit 2062 may be the same as or different from that of the operation display unit 62.

  The image processing unit 2046 performs an analysis process on the image data obtained by the reading operation of the reading unit 2025, and the ink discharge amount and the discharge direction are greatly deviated from the initial deviation nozzle and the design value that are out of the predetermined reference range. The initial defective nozzle is detected. The image processing unit 2046 includes a frequency analysis unit 2461, an initial deviation calculation unit 2462, and the like. The frequency analysis unit 2461 performs processing related to extraction of periodic density unevenness (corresponding to the gaps v21 to v23 in FIG. 3B) in the read image. The initial deviation calculation unit 2462 performs calculation processing for specifying information related to the initial deviation nozzle that causes the above-described periodic density unevenness. Further, the image processing unit 2046 can perform an initial defective nozzle detection operation based on non-periodic density unevenness (corresponding to the gap v11 in FIG. 3B).

  The output image generation unit 2045 generates inspection image data and outputs it to the head drive unit 531. When the inspection image data is vector image data or intermediate image data, the output image generation unit 2045 performs processing for converting the acquired data into raster image data via the intermediate image.

  The control unit 2040 includes a CPU 2041, a RAM 2042, a storage unit 2043, and the like. The CPU 2041 performs various arithmetic processing operations using the RAM 2042 as a working memory space.

The storage unit 2043 stores various control programs and setting data, as well as an execution program related to the nozzle initial deviation detection operation, setting data, an initial deviation nozzle detection result, and the like.
The setting data includes a characteristic frequency table 2433, and the detection result includes initial deviation nozzle area information 2432.

Next, the operation of detecting the presence of the initial deviation nozzle by the inspection apparatus 200 will be described.
In the inspection apparatus 200, the presence detection operation of the initial misaligned nozzle in the head unit 23 newly used in advance is performed before the head unit 23 is attached to the ink jet recording apparatus 100 or when the head unit 23 is replaced. Here, fine streaks and discharge amount due to periodic deviations in the discharge direction caused by problems in machine accuracy of the manufacturing apparatus and assembly apparatus when the nozzle array is formed or when a plurality of recording heads are attached to the support member. An operation for detecting density unevenness due to deviation will be described.

  As shown in FIG. 3B, in the recording head 232, when the nozzle position on the straight line 232b is shifted from the normal position by the minute shift amount dd, the nozzle of the predetermined density (halftone image) A streak (gap) may appear every six intervals 6d. Such minute landing position deviation is much smaller (gap) compared to the case where ink for one nozzle is completely lost due to ejection failure from the nozzle, and it is the same position according to landing error etc. Although it does not always appear every time, the probability of appearing in a predetermined spatial period is sufficiently high. In addition, depending on the relationship with the reading accuracy of the reading unit 25, it is often possible to detect the light and shade according to the gap, but streaks occur due to the deviation of the landing positions of the ink actually ejected from any nozzle. It is difficult to identify whether

  In the inkjet recording apparatus 100 of the present embodiment, the spectrum in the spectrum distribution in the frequency space corresponding to the periodic density unevenness by Fourier-transforming the profile (density distribution) in the width direction of the density value obtained in the output image. Detect intensity peaks. The appearance period of such a gap is mainly assumed to be determined based on the structure of the recording heads 231 and 232 and the head unit 23 and to be determined according to these manufacturing apparatuses and assembling apparatuses. The spatial frequency (feature frequency) that can appear in advance is held in the feature frequency table 2433 in advance. Next, an inverse Fourier transform is performed after masking the peak of the spectral intensity present at the characteristic frequency, and a correction profile (correction distribution) of density values in which the periodic unevenness is eliminated is obtained. Then, by comparing the original density distribution with the correction distribution and detecting a region where the density value (brightness value) has changed more than the reference, a range in which a periodic density change exists is specified. .

  FIG. 6 is a flowchart showing a control procedure by the control unit 2040 of the initial deviation detection process executed by the inspection apparatus 200 of the present embodiment.

This initial deviation detection process is activated by an input operation to the operation display unit 2062 by a person in charge of inspection.
When the initial deviation detection process is started, the control unit 2040 (CPU 2041) causes the output image generation unit 2045 to output a control signal for causing the head driving unit 531 to form an initial deviation evaluation image (inspection image). Then, ink is ejected from the head unit 23 (step S101). This evaluation image is a halftone image having a predetermined density, and the same appropriate frequency from each nozzle according to the ratio between the size of the ink ejected from each nozzle and landed on the recording medium P and the nozzle pitch, and the like. Thus, a halftone image in which ink is ejected can be obtained.

The control unit 2040 sends a control signal to the reading drive unit 2055 and operates the reading unit 2025 to read the evaluation image (step S102). The control unit 2040 calls and executes the initial deviation nozzle detection process, and identifies the presence area (initial deviation nozzle area) of the initial deviation nozzle using the read evaluation image data (step S103). The control unit 2040 stores the identified area in the storage unit 2043 as the initial deviation nozzle area information 2432 (step S104).
Then, the control unit 2040 ends the initial deviation detection process.

FIG. 7 is a flowchart showing a control procedure of the initial deviation nozzle detection process called in the initial deviation detection process.
When the initial deviation detection process is called, the control unit 2040 acquires read image data of the evaluation image read in the process of step S102 (step S301). The control unit 2040 obtains a frequency spectrum distribution by Fourier-transforming the spatial distribution (grayscale distribution) of the luminance values of the read image data in the width direction (step S302). At this time, when the read image data is acquired a plurality of times in the transport direction, the luminance values at the same position in the width direction may be integrated and used in the transport direction.

  The control unit 2040 refers to the feature frequency table 2433, selects one frequency (feature frequency) that is assumed as the appearance frequency of light and shade (step S303), and the spectrum value (in a predetermined frequency range including the frequency ( It is determined whether or not the peak value (maximum value) (which may be spectrum intensity, power, etc.) is equal to or greater than a predetermined value (a predetermined appearance criterion is satisfied) (step S304).

  If it is determined that the peak value is not greater than or equal to the predetermined value (“NO” in step S304), the process of the control unit 2040 proceeds to step S311. When it is determined that the peak value is greater than or equal to the predetermined value (“YES” in step S304), the control unit 2040 masks the spectrum value in the detected frequency band (step S305). That is, the control unit 2040 sets the spectrum value of the band including the selected frequency to “0” in the obtained frequency spectrum distribution.

  The control unit 2040 calculates a spatial distribution (corrected distribution) in the real space of the masked luminance value by performing inverse Fourier transform on the spectral distribution with the mask (step S306). The control unit 2040 compares the spatial distribution of the luminance measurement values acquired in step S301 with the correction distribution after masking obtained in the process of step S306, and the difference is greater than or equal to a predetermined reference value (predetermined difference condition). An area in which the occurrence has occurred is detected (step S307). In this detection operation, for example, the control unit 2040 calculates a moving average of luminance values for each predetermined width, and sequentially extracts regions where the difference or ratio of the moving average values is greater than a predetermined reference.

  The control unit 2040 determines whether or not an area where a difference has occurred is detected (step S308). If it is determined that it has not been detected (“NO” in step S308), the processing of the control unit 2040 proceeds to step S310. When it is determined that it has been detected (“YES” in step S308), the control unit 2040 displays information indicating the range of the difference (initially displaced nozzle area) and the color of the ink, and within the range. The maximum value of the density detection level obtained in step S304 is stored in the initial deviation nozzle area information 2432 (step S309). That is, when an area where a difference is detected among a plurality of different areas separated from each other is detected, the control unit 40 stores the initial deviation nozzle area information 2432 separately. Then, the process of the control unit 2040 proceeds to step S310.

  When the process proceeds to step S310, the control unit 2040 determines whether or not the area detection at the target frequency currently selected for all the image forming ranges and ink colors of the head unit 23 is completed (step S310). Step S310). If it is determined that the process has not been completed (“NO” in step S310), the process returns to step S308, and the difference in luminance value is continuously detected for another range.

If it is determined that all area detection has been completed (“YES” in step S310), the control unit 2040 determines whether or not all the characteristic frequencies stored in the characteristic frequency table 2433 have been selected ( Step S311). If it is determined that it has not been selected (“NO” in step S311), the control unit 2040 returns the process to step S303, selects another target frequency that has not been selected, and performs the processes in steps S304 to S310. repeat.
In other words, when areas having differences at different frequencies are detected, they are separately stored in the initial deviation nozzle area information 2432 regardless of whether or not the areas overlap.

  If it is determined that all the characteristic frequencies have been selected (“YES” in step S311), the control unit 2040 ends the initial deviation nozzle detection process and returns the process to the initial deviation detection process.

  The obtained initial deviation nozzle area information 2432 is copied to the storage unit 43 of the inkjet recording apparatus 100 as the corresponding head unit 23 is attached to the inkjet recording apparatus 100. In addition, the head unit 23 has an initial deviation information storage unit separately from the storage unit 43, and initial deviation nozzle area information is written and held in the initial deviation information storage unit when the initial deviation detection process is executed. Also good.

FIG. 8 is a diagram illustrating an example of inspection data of the inspection apparatus 200 according to the present embodiment.
FIG. 8A is a diagram illustrating a luminance distribution related to a light and shade spatial distribution.
In FIG. 8A, the solid line indicates the measured value of the density distribution read by the reading unit 2025. In the density distribution, a slight increase / decrease is observed, and a portion with a high luminance value indicates that ink ejection is small or missing.

FIG. 8B is a diagram showing the amplitude of the spectral intensity with respect to the value (lp / mm) corresponding to the spatial frequency, that is, the number of nozzles per 1 mm (number of lines formed by the nozzles).
Here, peaks p1 and p2 are seen at a position of about 3.9 lp / mm and a multiple of about 7.8 lp / mm. A value of about 3.9 lp / mm corresponds to a nozzle spacing of 12 × 21.17 μm, that is, there is a light and shade at every 12 nozzles in a 1200 dpi nozzle arrangement (every 6 nozzles in a 600 dpi nozzle arrangement). It has been shown.

  As shown in FIG. 8 (c), a spectral distribution masking the spectral value in the range f1 including 3.9 lp / mm is generated, and this spectral distribution is subjected to inverse Fourier transform, whereby the dotted line in FIG. 8 (a). A density distribution after masking is obtained.

  When the measured density distribution (solid line) in FIG. 8A is compared with the density distribution after masking (dotted line), a significant decrease is seen in the amplitude of the density distribution after masking in the region (s). Accordingly, in this area, it is identified that an initial deviation occurs every 12 nozzles (1200 dpi).

Next, the nozzle defect detection operation in the inkjet recording apparatus 100 of the present embodiment will be described.
FIG. 9 is a diagram illustrating an example of a defect presence / absence detection image for detecting the presence / absence of a discharge defect and an example of a defective nozzle specifying image for identifying a discharge defect nozzle when a discharge defect is detected.
As shown in FIG. 9A, normally, when a normal formation target image F (output target image) is formed on the recording medium P, defective presence / absence detection images C21 to C24 ( A predetermined test image) is formed, and it is determined whether or not each image F is normally output (whether there is a discharge abnormality) by the defect presence / absence detection images C21 to C24.

  As shown in FIG. 9B, each of the defect presence / absence detection images C21 to C24 is a halftone image (an image having a predetermined density) of each color of CMYK. This halftone image is formed by ejecting ink from all nozzles at a substantially equal frequency, and when ejection failure occurs from any nozzle, it corresponds to ink loss from the nozzle. The density decreases at the position in the width direction. As a result, the reading unit 25 detects density unevenness caused by an increase in the luminance value at the position according to the background color (usually white of the recording medium P). The raster image data of the defect presence / absence detection images C21 to C24 is supplemented by peripheral nozzles with respect to the ejection defects of the ejection failure nozzles already identified and stored in the ejection failure nozzle list 431 together with the image F to be formed. It can be done. In this way, by adjusting the ink ejection of the ejection failure nozzle and the surrounding nozzles (normally, the ink from the ejection failure nozzle itself is not ejected), an image is recorded on the recording medium using the raster image data that has been complemented. By forming, only density unevenness of newly generated (and / or recovered) defective nozzles is detected, and an abnormality in image quality for the image F actually formed and output is detected.

When an abnormality relating to density unevenness is detected in the defect presence / absence detection image, a defective nozzle specifying image for specifying a defective discharge nozzle (defective nozzle) that causes the abnormality is formed.
As shown in FIG. 9C, in the defective nozzle specifying image L, for example, a straight line corresponding to the number of nozzles is formed in a ladder shape so that the landing positions of the ink ejected from each nozzle are separated. When a straight line is not formed at an appropriate position, it is determined that a nozzle corresponding to the position where the straight line is not formed has an ejection failure. In this case, the nozzles that form each straight line of the defective nozzle specifying image L may be all the nozzles of the corresponding head unit 23, or a part including a range in which an abnormality is detected in the defective presence / absence detection image. However, the latter can reduce the amount of ink consumed, and the size of the defective nozzle specific image L can be reduced.

  Here, even when a gap or unevenness occurs due to the above-described initial deviation, the luminance value at the position corresponding to the gap or unevenness in the defect presence / absence detection image rises, and depending on the size of the gap, a subsequent ejection failure may occur. May be detected together. Therefore, in the ink jet recording apparatus 100 of the present embodiment, the detection reference in the initial deviation nozzle area is made stricter than that outside the initial deviation nozzle area, thereby suppressing unnecessary redetection of gaps and unevenness due to the initial deviation nozzle area. .

FIG. 10 is a flowchart illustrating a control procedure by the control unit 40 of the ejection failure detection process executed in the inkjet recording apparatus 100 of the present embodiment.
This ejection failure detection process is executed when normal image recording is performed in the inkjet recording apparatus 100.

  In the ejection failure detection process, the control unit 40 forms an image on the recording medium P by the head drive unit 531 by adding the defect presence / absence detection image to the margin and performing the above-described complement processing on the normal image. This is performed (step S501). The control unit 40 causes the reading unit 25 to read the formed defect presence / absence detection image, obtains the luminance value distribution of the read image data as a density distribution, and detects abnormality of the defect presence / absence detection image, that is, a predetermined reference level. The above uneven density (luminance value) is detected (step S502).

  The control unit 40 determines whether an abnormality is detected in the defect presence / absence detection image (step S503). If it is determined that it has not been detected (“NO” in step S503), the processing of the control unit 40 returns to step S501 and performs processing related to image formation of the next normal image and defect presence / absence detection image.

When it is determined that an abnormality is detected in the defect presence / absence detection image (“YES” in step S503), the control unit 40 refers to the initial deviation nozzle area information 432 and the detected range is the initial deviation nozzle area. It is determined whether it is within (step S504). If it is determined that it is not within the initial deviation nozzle area (“NO” in step S504), the processing of the control unit 40 proceeds to step S507. If it is determined that it is within the initial deviation nozzle area (“YES” in step S504), the abnormality detection reference level (discharge abnormality detection reference) is changed (step S505), and an abnormality is detected again in the defect presence / absence detection image. It is determined whether or not it is detected (step S506).
At this time, depending on the resolution of the line sensor of the reading unit 25, as the changed detection reference level, in addition to or instead of simply changing the value of the difference in light and shade, the width of the changed portion of light and shade is added as a condition. I can do it. If the resolution of the line sensor is not more than several times larger than the nozzle pitch, when the ink from the ejection failure nozzle is not ejected, the brightness value obtained by the two adjacent image sensors continues to show a normal part. While the luminance value obtained by the imaging device is higher than that obtained by the imaging device, the small gap related to the initial deviation described above is sufficiently narrower than the resolution of the line sensor, so the luminance values obtained by the two imaging devices are continuously obtained. Do not change.

  If it is determined that no abnormality is detected (“NO” in step S506), the process of the control unit 40 returns to step S501. If it is determined that an abnormality has been detected, the process of the control unit 40 proceeds to step S507.

  When the process proceeds from step S504 and step S506 to step S507, the control unit 40 interrupts the normal formation target image formation and causes the image forming unit 20 to form a defective nozzle specifying image (step S507). The control unit 40 causes the reading unit 25 to read the defective nozzle identification image, and identifies the defective ejection nozzle that has caused the ejection failure from the read defective nozzle identification image (step S508). The control unit 40 updates the ejection failure nozzle list 431 including the identified ejection failure nozzle (step S509).

  The control unit 40 determines whether or not the ejection failure nozzles (defective nozzle detection status) listed in the ejection failure nozzle list 431 are within the reference range (step S510). As the reference range, the number of defective ejection nozzles is equal to or less than a preset upper limit value according to the required image quality of the formed image and the total number of nozzles, or a predetermined number (for example, two) of defective ejection nozzles in the width direction. It is determined that it does not exist continuously.

  If it is determined that it is within the reference range (“YES” in step S510), the process of the control unit 40 returns to step S501. When it is determined that it is not within the reference range (a predetermined first condition is satisfied or a predetermined second condition is satisfied) (“NO” in step S510), the control unit 40 determines that the current ejection failure nozzle It is determined whether or not the stored contents of the list 431 are after execution of the cleaning operation (after the recovery operation) (step S511). If it is determined that the cleaning operation is not performed (“NO” in step S511), the control unit 40 operates the cleaning unit 27 to perform the nozzle surface cleaning operation (step S512). Then, the process of the control unit 40 proceeds to step S507.

  When it is determined that the cleaning operation has been performed ("YES" in step S511), the control unit 40 causes the notification unit 63 to perform a predetermined notification operation or causes the operation display unit 62 to perform a predetermined operation. By performing a warning operation, notification indicating an abnormal state of the head unit 23 is performed (step S513). Alternatively, the control unit 40 may cause an e-mail to be transmitted to the set administrator via the communication unit 61. Then, the control unit 40 ends the ejection failure detection process.

  FIG. 11 is a flowchart illustrating a control procedure of another example of ejection failure detection processing executed by the inkjet recording apparatus 100.

  In this ejection failure detection processing, the processing in step S521 is added between the processing in steps S501 and S502, and the processing in steps S504 to S506 is omitted. The same processing contents are denoted by the same reference numerals, and description thereof is omitted.

  After the processing of step S501, the control unit 40 acquires the read data of the defect presence / absence detection image by the reading unit 25 and refers to the initial shift nozzle area information 432 and is stored in the initial shift nozzle area information 432. The information on the spatial frequency related to the appearance of the initially displaced nozzle is acquired. The control unit 40 performs the process of masking (suppressing) the shading change corresponding to the spatial frequency in the read data, and then detects the presence or absence of ejection failure (step S521). The control unit 40 masks the change in shading due to the spatial frequency by performing processing (trap processing) on the read data using a trap filter (band elimination filter) to attenuate only the signal in the band including the spatial frequency. Data of correction distribution (correction data) is generated. Then, the process of the control unit 40 proceeds to step S502. Note that the control unit 40 may limit the generation range of the correction distribution to a part of the acquired density distribution according to the range of the area where the initial deviation nozzle is detected.

  On the other hand, when it is determined that a density abnormality equal to or higher than the reference is detected in the defect presence / absence detection image (corrected image) corrected in the determination processing in step S503 ("YES" in step S503), the control unit 40 performs processing. Is shifted to step S507.

  In other words, the control unit 40 generates a correction distribution in which the influence on the density distribution due to the initial deviation is suppressed in advance, so that the abnormality determination criterion according to the detection region is not changed when abnormality is detected from the defect presence / absence detection image. .

As described above, the inkjet recording apparatus 100 according to the present embodiment includes the head unit 23 in which a plurality of nozzles are arranged and each ejects ink from the openings of the plurality of nozzles, and among the plurality of nozzles, the ink ejection amount and An image recorded by the head unit 23 and a storage unit 43 that holds initial deviation nozzle area information 432 relating to appearance characteristics such as the presence area and spatial frequency of an initial deviation nozzle that has caused an initial deviation in at least one of the ink ejection directions. A reading unit 25 for reading and a control unit 40 are provided. The control unit 40 detects the presence / absence of ink ejection abnormality from the defect presence / absence detection image read by the reading unit 25 as ejection abnormality detection means. At this time, the CPU 41 as the discharge abnormality detection means detects a discharge abnormality that is not caused by the initial deviation based on the initial deviation nozzle area information 432 held by the storage unit 43.
In this way, by separating the nozzles that are initially displaced from the detection of the subsequent ejection failure, operations such as unnecessary cleaning, ink discharge operation, and replacement of the head unit 23 are suppressed. Further, since the nozzle specifying process associated with the detection of a slight initial deviation is omitted, it is possible to suppress interruption of image formation and consumption of ink and recording medium related to a specific operation of specifying a difficult nozzle. Therefore, it is possible to suppress a decrease in operation efficiency and cost performance due to the initial displacement of the nozzle.

In addition, the initial deviation nozzle area information 432 includes area information indicating the appearance range of the initial deviation, and the control unit 40 serving as the discharge abnormality detecting unit determines whether the initial deviation appears within the initial deviation appearance range based on the area information. The ejection abnormality detection standard is made different from the outside of the appearance range.
In this way, by suppressing the influence on the detection of the initial deviation nozzle only in the range where the initial deviation nozzle appears, the possibility of unnecessary detection of the initial deviation is suppressed, and the detection failure of the subsequent ejection failure occurs. Can be difficult.

  Further, the area information includes detection level information of the initial deviation, and the control unit 40 as the discharge abnormality detection unit determines a discharge abnormality detection standard in which the initial deviation is not detected as the discharge abnormality based on the detection level information. . In this way, it is possible to perform detection by appropriately classifying a slight initial deviation and a normal subsequent ejection failure using a specific initial deviation detection level.

The defect presence / absence detection image is an image having a predetermined density (halftone image), and the control unit 40 serving as a discharge abnormality detection unit determines presence / absence of discharge abnormality based on density unevenness of the defect presence / absence detection image.
That is, since it is possible to detect the presence or absence of ejection abnormality flexibly according to the appearance of initial deviation without taking up a place with an easy image, waste can be reduced.

Further, the initial deviation nozzle area information 432 includes information on the spatial frequency related to the periodic appearance characteristics of the detected initial deviation nozzle, and the CPU 41 as the discharge abnormality detection unit detects the defect read by the reading unit 25. The presence / absence of ejection abnormality is determined based on the density unevenness of the correction distribution (correction data) obtained by performing processing for suppressing the density change of the spatial frequency for the data of the presence / absence detection image.
As described above, since the periodic initial deviation relating to the manufacture and arrangement of the recording head and the like in the head unit 23 is appropriately cut and the ejection abnormality is determined based on the correction data in which the influence of the initial deviation is reduced, Subsequent ejection defects can be detected while more appropriately eliminating the influence of initial deviation.

  In addition, the control unit 40 operates as a recording control unit that records a defect presence / absence detection image corresponding to the recording operation by the head unit 23 of the output target image related to the acquired print job. In this way, by forming a test image that acquires only the presence or absence of ejection failure in the margin together with the output target image, it is possible to reliably determine the image quality failure of the output target image while preventing wasteful use of the recording medium. It is possible to determine a defective image related to an ink ejection defect.

Further, when a discharge abnormality not detected due to initial deviation is detected, a defective nozzle specifying image for specifying a defective nozzle causing the discharge abnormality is formed by the head unit 23, and the control unit 40 is formed. The defective nozzle specifying unit operates as defective nozzle specifying means for specifying a defective nozzle based on the data read by the reading unit 25 of the defective nozzle specifying image.
As described above, since the defective nozzle identification image is generated and the defective nozzle is specified only when it is necessary due to the occurrence of the subsequent ejection defect, the time for identifying the defective ejection nozzle and the waste of the recording medium can be prevented appropriately. An ejection failure nozzle can be detected.

  Further, the control unit 40 adjusts the ink ejection from the specified ejection failure nozzle and the peripheral nozzles of the ejection failure nozzle to form an output target image in which the ink ejection failure of the ejection failure nozzle is complemented by the head unit 23. It works as a complementary means. In this way, ink that is not ejected normally due to defective ejection nozzles is appropriately handled by complementary operations from surrounding nozzles, and those that do not allow improvement in image quality even if they are complemented as minor initial deviations By removing from the complement target, it is possible to preferentially supplement the defective nozzles that really need to be complemented. Accordingly, it is possible to continue the formation of an image satisfying a desired image quality standard by reducing the frequency of occurrence of unnecessary cleaning operations and the like.

In addition, the cleaning unit 27 that recovers the ink ejection failure of the ejection failure nozzle is provided, and the control unit 40 performs a recovery control unit that operates the cleaning unit 27 when the detection status of the ejection failure nozzle satisfies the predetermined first condition. Works as.
Therefore, it is possible to eliminate the initial deviation nozzle that is not improved by the normal cleaning, and to perform the cleaning operation at an appropriate interval and timing according to the occurrence state of the subsequent ejection defective nozzle recovered by the cleaning. Cleaning can be reduced.

In addition, the control unit 40 as a recovery control unit includes a notification unit 63 and an operation display unit 62 that perform a notification operation, and the detection status of defective ejection nozzles after the recovery operation by the cleaning unit 27 satisfies a predetermined second condition. In addition, the notification unit 63 and the operation display unit 62 are caused to perform a predetermined notification operation.
Therefore, when the nozzle that should be recoverable without the influence of the initial deviation is not sufficiently recovered by the cleaning operation, the head unit 23 can be replaced at an appropriate timing by informing the user to that effect. I can do it.

In addition, the head unit 23 extends over the width in which the image can be formed on the recording medium in the width direction perpendicular to the relative movement direction (that is, the conveyance direction) between the head unit 23 and the recording medium on which the image is recorded. And a line head capable of ejecting ink without relative movement in the width direction between the recording medium 23 and the recording medium.
As described above, in the line head in which the landing position of the ink ejected from the nozzle opening portion is linearly moved relative to the recording medium, particularly fine density unevenness is likely to occur. Thus, it is possible to perform a discharge failure detection operation, a recovery operation corresponding to this, and a head replacement.

  The head unit 23 includes a plurality of recording heads 231 and 232. In this way, when there is a deviation in the position of the nozzle opening in units of recording heads, a slight initial deviation or a periodic initial deviation that limits the area tends to occur. And discharge failure can be appropriately classified and discharge failure can be detected and dealt with efficiently.

The head unit 23 has two recording head groups 231T and 232T in which the openings of the plurality of nozzles are arranged so that the width direction component in the interval between the openings of the plurality of nozzles is a predetermined arrangement interval 2d. And
The two recording head groups 231T and 232T are relatively arranged so that the width direction component in the interval between the nozzle openings as a whole is one half of the arrangement interval 2d, that is, the interval d.
Alternatively, the head unit 23 is further paired with nozzle openings provided at intervals of 6d on three lines of straight lines 231a, 231b, 231c (232a, 232b, 232c), which are shifted from each other by an interval of 2d in the width direction. The recording heads 231 and 232 that are to be arranged are shifted by a distance d in the width direction, so that the nozzle openings of a total of six nozzle opening rows in the transport direction as a whole are arranged at an interval 6d in each nozzle opening row. Relative to each other with an interval d of 1/6.
In such an arrangement, periodic initial deviations are likely to appear due to limitations in manufacturing machine accuracy, etc., and therefore, by applying the present invention, the effects of such periodic initial deviations are effectively eliminated. As a result, it is possible to efficiently and appropriately detect and deal with ejection failure nozzles.

  Further, since the nozzles belonging to the respective recording head groups 231T and 232T are provided in the different recording heads 231 and 232, the influence of mounting (assembly) errors may appear in such an arrangement. As a result, the initial deviation in each of the recording head groups 231T and 232T is likely to appear more clearly periodically. Therefore, by applying the present invention, it is possible to more effectively eliminate the influence of such a periodic initial deviation, and to detect and deal with a defective ejection nozzle efficiently and appropriately.

In addition, the ink discharge abnormality detection method of the inkjet recording apparatus 100 of the present embodiment including the head unit 23 in which a plurality of nozzles are arranged and each discharges ink from the openings of the plurality of nozzles is recorded by the head unit 23. A reading step for reading a defect presence / absence detection image, and a discharge abnormality detection step for detecting presence / absence of ink ejection abnormality from the defect presence / absence detection image read in the reading step. On the basis of the initial deviation information relating to the appearance characteristics such as the presence area and the spatial frequency of the initial deviation nozzle that has caused the initial deviation in at least one of the ejection amount and the ink ejection direction, the ejection abnormality not depending on the initial deviation is detected.
In this way, by detecting only the defective ejection nozzles using the initial deviation information, it is possible to more efficiently implement the countermeasures related to the ejection defects and suppress the decrease in the operation efficiency of the inkjet recording apparatus 100.

The initial deviation detection method for detecting the initial deviation related to the ink ejection of each nozzle in the head unit 23 of the present embodiment in which a plurality of nozzles are arranged and ejects ink from the openings of the plurality of nozzles includes a plurality of nozzles. The detection image recording step for recording a halftone image of a predetermined density as a detection image by the above, the image reading step for reading the density distribution of the detection image recorded in the detection image recording step, and the detection read in the image reading step A frequency detection step for detecting a frequency component related to the spatial distribution of the gray level of the image for use, and an appearance characteristic of the gray level distribution of the frequency at which the peak value of the luminance value at a certain frequency component detected in the frequency detection step is greater than or equal to a predetermined value An initial deviation information specifying step for specifying initial deviation information (that is, frequency, area and peak value).
In this way, instead of specifying the initial deviation nozzles individually, the initial deviation information of the periodicity is detected in advance, so that processing that requires labor and cost for detection such as minor initial deviations, particularly ejection direction deviations, is performed. Necessary information can be easily acquired without performing the process. Further, by efficiently performing the defective ejection nozzle detection operation in the head unit 23 based on the information acquired in this way, it is possible to suppress a decrease in the operational efficiency of the inkjet recording apparatus 100.

  Further, the initial deviation information specified in the initial deviation information specifying step includes area information indicating the appearance range of the detected initial deviation. Thus, by including the range information of the initial deviation that occurs locally, such as the recording head unit, it becomes possible to detect the ejection failure nozzle in consideration of the influence of the initial deviation only in the appearance range, and the normal ejection The accuracy related to detection of defective nozzles is not reduced more than necessary.

Further, in the initial deviation information specifying step, the gray level distribution obtained in the image reading step is compared with the correction distribution obtained by removing the frequency component related to the gray level distribution satisfying the predetermined appearance criterion from the gray level distribution. A range that does not match within the conditions is specified as the appearance range of the initial deviation.
Thus, by performing relative comparison, the appearance range can be specified easily and reliably.

  Further, in the frequency detection step, a frequency indicating a spectrum intensity equal to or higher than a predetermined reference value is detected in the spectrum distribution obtained by Fourier transforming the grayscale distribution, and in the initial deviation information specifying step, the detected frequency in the spectrum distribution is detected. The correction distribution is obtained by performing inverse Fourier transform while masking the spectrum of. In this way, a correction distribution for detection and comparison related to periodicity is generated in the frequency space using the Fourier transform, and the range in which the initial deviation nozzle actually exists is obtained in the real space. It is possible to efficiently acquire necessary information and appropriately acquire the appearance range of the initial deviation.

Further, in the frequency detection step, the spatial frequency related to the structure of the head unit 23 and the frequency corresponding to the spatial frequency related to the manufacture of the head unit 23 are specified in advance as characteristic frequencies that can occur in the gray distribution, and in the initial deviation information specifying step, The initial deviation information is specified when the light and shade distribution at the characteristic frequency satisfies a predetermined appearance criterion.
Therefore, it is possible to separate the influence of the nozzle having a non-periodic and serious problem due to the initial ejection failure from the detection of the initial deviation, and appropriately acquire the periodic initial deviation and reflect it in the detection of the ejection failure nozzle.

The head unit 23 has recording head groups 231T and 232T at a plurality of different positions in the transport direction along the outer peripheral surface of the image forming drum 21 of the recording medium for recording an image, and the recording head groups 231T and 232T. Are arranged so that the arrangement interval in the width direction perpendicular to the conveying direction of the plurality of nozzle openings provided in each is narrower than the arrangement interval 2d of the nozzle openings in each of the recording head groups 231T and 232T. The characteristic frequency includes an arrangement interval 2d of the nozzle openings of each of the recording head groups 231T and 232T.
Thus, when the nozzle arrangement is periodic according to the arrangement structure of the recording head or the like, the initial deviation is likely to occur according to the period, and the initial deviation can be easily and effectively applied by applying the present invention. Can be used to detect defective nozzles.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in the above-described embodiment, the operation of detecting and responding to a minor one that appears periodically as an initial deviation and does not need complementation has been described. Similarly, an initial defective nozzle that needs to be complemented may be stored as an initial misaligned nozzle. In this case, the initial defective nozzle itself may be specified in advance using not only the appearance area information but also the defective nozzle specifying image or the like, and stored in the initial misaligned nozzle area information. Since such initial defective nozzles are usually difficult to recover by applying the conventional recovery technique, for example, in a determination process related to whether or not cleaning can be performed in step S510, etc. Can be handled.

  In addition, for example, an initial deviation nozzle that appears aperiodically in units of a head module or a recording head and does not need to be complemented is caused to retain appearance area information and detection level information in the same manner as those that appear periodically. I can do it. Such an aperiodic and slight initial deviation is not a frequency analysis, for example, a region where the density is significantly different from other regions by a moving average of a light and shade distribution, or an inspector detects a test image. The area may be determined by visually recognizing.

  Further, in the above embodiment, the initial deviation nozzle area information 432 holds information on the detection level at the time of initial deviation nozzle area detection, and the ejection abnormality detection reference in the initial deviation nozzle area is changed according to the detection level. However, it may be changed uniformly.

  In the above embodiment, the ejection abnormality is detected using the density unevenness of the halftone image. However, if the test image can check the density unevenness within a predetermined range due to the ejection abnormality, the halftone image is detected. The predetermined pattern image or the like may be formed.

  In the above-described embodiment, the reference for starting the cleaning operation for the subsequent defective nozzle and the reference for performing the notification operation for prompting replacement are the same, but different criteria can be used.

  In the above embodiment, the inkjet recording apparatus 100 that includes a line head and discharges ink from a fixed line head while transporting a recording medium has been described as an example. However, an image is scanned while the head unit 23 is scanned. Even in the case of an ink jet recording apparatus that forms a single-pass type, the present invention can be similarly applied. Further, if the arrangement interval in the width direction perpendicular to the recording medium conveyance direction and the direction perpendicular to the scanning direction of the head unit is uniform, the arrangement of the openings of the nozzles in the conveyance direction and the scanning direction is as follows: It may be determined as appropriate. For example, the openings of the nozzles may be arranged one-dimensionally at equal intervals obliquely with respect to the transport direction.

  Further, the arrangement of the nozzle openings in the head unit 23 and the number and arrangement of the recording heads are not limited to those described in the above embodiment. For example, the recording heads 231 and 232 do not have to be configured in pairs, and the characteristic frequency may be appropriately determined according to the arrangement.

  In the above embodiment, the ejection failure detection operation is performed by the inkjet recording apparatus 100. However, the ejection failure may be detected by using an external reading device or detection device. On the other hand, when the inkjet recording apparatus 100 has a configuration necessary for detecting the initial deviation, or when information can be exchanged with the necessary hardware via the communication unit 61, the head unit in the inkjet recording apparatus 100 is used. The initial misalignment nozzle may be detected after 23 is attached.

  In the above-described embodiment, the nozzle surface cleaning using the cleaning unit 27 is described as an example of a method for recovering a defective ejection nozzle. However, the present invention is not limited to this. For example, clogging in the nozzle can be used together by a flushing operation in which ink is ejected at a pressure higher than usual.

The setting and generation of the complementary image is performed by the external device by outputting the information on the obtained ejection failure nozzle to the outside, and the complemented raster image data is acquired and the inkjet recording apparatus 100 acquires the image. A recording operation may be performed.
In addition, specific details such as the configuration, control contents, and procedures shown in the above embodiment can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 10 Medium supply part 11 Paper feed tray 12 Conveyance part 121, 122 Roller 123 Belt 20 Image formation part 21 Image formation drum 22 Delivery unit 221 Claw part 222 Delivery drum 23 Head unit 231 Recording head 231a-231c Straight line 231T Recording head group 232 Recording Heads 232a to 232c Straight line 232T Recording head group 235 Heater 24 Irradiation unit 25 Reading unit 26 Delivery unit 261, 262 Roller 263 Belt 264 Delivery roller 27 Cleaning unit 30 Medium discharge unit 31 Paper discharge tray 40 Control unit 41 CPU
42 RAM
43 storage unit 431 ejection failure nozzle list 432 initial deviation nozzle area information 51 transport drive unit 531 head drive unit 535 heater drive unit 54 irradiation drive unit 55 read drive unit 57 cleaning drive unit 61 communication unit 62 operation display unit 63 notification unit 69 bus DESCRIPTION OF SYMBOLS 100 Inkjet recording device 200 Inspection apparatus 2024 Irradiation part 2025 Reading part 2040 Control part 2041 CPU
2042 RAM
2043 Storage unit 2432 Initial deviation nozzle area information 2433 Characteristic frequency table 2045 Output image generation unit 2046 Image processing unit 2461 Frequency analysis unit 2462 Initial deviation calculation unit 2051 Transport drive unit 2054 Irradiation drive unit 2055 Read drive unit 2061 Communication unit 2062 Operation display unit P Recording medium

Claims (22)

A recording unit in which a plurality of nozzles are arranged and each ejects ink from openings of the plurality of nozzles;
Adjustment information storage means for holding initial deviation information relating to the appearance characteristics of an initial deviation nozzle that has produced an initial deviation in at least one of the ink ejection amount and the ink ejection direction among the plurality of nozzles;
Reading means for reading an image recorded by the recording means;
An ejection abnormality detecting means for detecting the presence or absence of an ink ejection abnormality from a predetermined test image read by the reading means;
With
The discharge abnormality detection means detects discharge abnormality not based on the initial deviation based on the initial deviation information held by the adjustment information storage means ,
The initial deviation information includes area information indicating the appearance range of the initial deviation,
The ink jet recording apparatus according to claim 1, wherein the discharge abnormality detecting means makes the discharge abnormality detection reference different between the appearance range of the initial deviation and the outside of the appearance range of the initial deviation based on the area information . A recording unit in which a plurality of nozzles are arranged and each ejects ink from openings of the plurality of nozzles;
Adjustment information storage means for holding initial deviation information relating to the appearance characteristics of an initial deviation nozzle that has produced an initial deviation in at least one of the ink ejection amount and the ink ejection direction among the plurality of nozzles;
Reading means for reading an image recorded by the recording means;
An ejection abnormality detecting means for detecting the presence or absence of an ink ejection abnormality from a predetermined test image read by the reading means;
With
The discharge abnormality detection means detects discharge abnormality not based on the initial deviation based on the initial deviation information held by the adjustment information storage means ,
The test image is an image having a predetermined density,
The initial deviation information includes spatial frequency information related to the periodic appearance characteristics of the detected initial deviation nozzle,
The ejection abnormality detecting means determines whether or not there is an ejection abnormality based on density unevenness of correction data obtained by performing processing for suppressing density change of the spatial frequency for the test image data read by the reading means. An ink jet recording apparatus. The area information includes detection level information by the reading means of the initial deviation,
Said ejection failure detecting means is the detection level based on the information, the initial deviation the discharge not detected as abnormal said ejection failure detecting reference and wherein the determining the claims 1 An ink jet recording apparatus according. The test image is an image having a predetermined density,
It said ejection failure detecting means is claim 1 or 3 Symbol mounting of the ink jet recording apparatus, characterized in that to determine the presence or absence of the ejection abnormality based on the density unevenness of the test image. The test image is an image having a predetermined density,
The initial deviation information includes spatial frequency information related to the periodic appearance characteristics of the detected initial deviation nozzle,
The ejection abnormality detecting means determines whether or not there is an ejection abnormality based on density unevenness of correction data obtained by performing processing for suppressing density change of the spatial frequency for the test image data read by the reading means. an ink jet recording apparatus according to claim 1 or 3, wherein the to.   The recording control unit according to claim 1, further comprising: a recording control unit configured to record the test image in response to a recording operation performed by the recording unit on the output target image related to the acquired image formation command. Inkjet recording apparatus. When a discharge abnormality not due to the initial deviation is detected, a defective nozzle specifying image for specifying a defective nozzle causing the discharge abnormality is formed by the recording unit, and the formed defective nozzle specifying image is formed. The inkjet recording apparatus according to claim 1, further comprising: a defective nozzle specifying unit that specifies the defective nozzle based on data read by the reading unit.   Complementing means for adjusting the ink ejection from the identified defective nozzle and the peripheral nozzles of the defective nozzle to form an output target image supplemented with the defective ink ejection of the defective nozzle by the recording means, An ink jet recording apparatus according to claim 7. Recovery means for recovering defective ink ejection of the defective nozzle;
Recovery control means for performing the operation of the recovery means when the detection status of the defective nozzle satisfies a predetermined first condition;
An ink jet recording apparatus according to claim 7 or 8, further comprising: A notification means for performing a notification operation;
The recovery control unit causes the notification unit to perform a predetermined notification operation when the detection state of the defective nozzle after the recovery operation by the recovery unit satisfies a predetermined second condition. 9. An ink jet recording apparatus according to item 9.   The recording means includes the width between the recording means and the recording medium in a width direction perpendicular to the relative movement direction of the recording means and the recording medium on which an image is recorded, over an image formable width with respect to the recording medium. The inkjet recording apparatus according to claim 1, further comprising a line head capable of ejecting ink without performing relative movement in a direction.   The inkjet recording apparatus according to claim 1, wherein the recording unit includes a plurality of recording heads. The recording means has a predetermined number of ink ejection blocks in which a plurality of nozzle openings are arranged so that a predetermined direction component in a gap between the openings of the plurality of nozzles is a predetermined arrangement interval,
2. The predetermined number of ink ejection blocks are relatively arranged so that the predetermined direction component in the interval between the openings of the nozzles is a predetermined number of the arrangement interval as a whole. The inkjet recording apparatus as described in any one of -12.   14. The inkjet recording apparatus according to claim 13, wherein the nozzles belonging to different ink ejection blocks are provided in different recording heads. An ink ejection abnormality detection method for an inkjet head comprising a plurality of nozzles arranged and a recording means for ejecting ink from the openings of the plurality of nozzles,
A reading step of reading a predetermined test image recorded by the recording means;
An ejection abnormality detecting step for detecting the presence or absence of an ink ejection abnormality from the predetermined test image read in the reading step;
Including
In the ejection abnormality detection step, the initial deviation is determined based on initial deviation information related to the appearance characteristic of an initial deviation nozzle that has an initial deviation in at least one of the ink ejection amount and the ink ejection direction among the plurality of nozzles. Detects abnormal discharge and
The initial deviation information includes area information indicating the appearance range of the initial deviation,
In the ejection abnormality detection step, an ejection abnormality detection reference is made different between the appearance range of the initial deviation and the outside of the appearance range of the initial deviation based on the area information . An ink ejection abnormality detection method for an inkjet head comprising a plurality of nozzles arranged and a recording means for ejecting ink from the openings of the plurality of nozzles,
A reading step of reading a predetermined test image recorded by the recording means;
An ejection abnormality detecting step for detecting the presence or absence of an ink ejection abnormality from the predetermined test image read in the reading step;
Including
In the ejection abnormality detection step, the initial deviation is determined based on initial deviation information related to the appearance characteristic of an initial deviation nozzle that has an initial deviation in at least one of the ink ejection amount and the ink ejection direction among the plurality of nozzles. Detects abnormal discharge and
The test image is an image having a predetermined density,
The initial deviation information includes spatial frequency information related to the periodic appearance characteristics of the detected initial deviation nozzle,
In the ejection abnormality detection step, the presence / absence of the ejection abnormality is determined based on density unevenness of correction data obtained by performing processing for suppressing density change of the spatial frequency on the data of the test image read in the reading step. An ink ejection abnormality detection method comprising: An initial deviation detection method for detecting an initial deviation related to ink ejection of each nozzle in a recording unit in which a plurality of nozzles are arranged and ejects ink from openings of the plurality of nozzles,
A detection image recording step of recording a halftone image of a predetermined density as a detection image by the plurality of nozzles;
An image reading step for reading a density distribution of the detection image recorded in the detection image recording step;
A frequency detection step for detecting a frequency component related to a spatial distribution of light and shade of the detection image read in the image reading step;
An initial deviation information identifying step for identifying initial deviation information relating to the appearance characteristics of the density distribution of the frequency satisfying the predetermined appearance criterion detected in the frequency detection step;
An initial deviation detecting method comprising: 18. The initial deviation detection method according to claim 17, wherein the initial deviation information specified in the initial deviation information specifying step includes area information indicating an appearance range of the detected initial deviation. In the initial deviation information specifying step, the gray level distribution obtained in the image reading step is compared with a correction distribution obtained by removing frequency components related to the gray level distribution satisfying the predetermined appearance criterion from the gray level distribution. 19. The initial deviation detection method according to claim 18 , wherein a range that does not match within the difference condition is specified as an appearance range of the initial deviation. In the frequency detection step, a frequency indicating a spectral intensity equal to or higher than a predetermined reference value is detected in a spectral distribution obtained by Fourier transforming the gray distribution,
The initial deviation detection method according to claim 19, wherein, in the initial deviation information specifying step, the correction distribution is acquired by performing inverse Fourier transform while masking a spectrum of the detected frequency in the spectrum distribution. . In the frequency detection step, a spatial frequency related to the structure of the recording means and a frequency corresponding to the spatial frequency related to the manufacture of the recording means are specified in advance as characteristic frequencies that can occur in the gray distribution,
In the initial displacement information specifying step, according to any one of claims 17 to 20, characterized in that the shading distribution in the characteristic frequency to identify the initial shift information if it meets the predetermined appearance criteria Initial deviation detection method. The recording means has ink ejection blocks at a plurality of different positions in a predetermined transport direction of a recording medium for recording an image;
The plurality of ink discharge blocks are arranged in the width direction perpendicular to the transport direction between the plurality of nozzle openings provided in each of the plurality of nozzles. It is arranged to narrower than,
The initial deviation detection method according to claim 21 , wherein the characteristic frequency includes an arrangement interval of openings of the plurality of nozzles in each of the ink ejection blocks.

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