JP2019111693A - Relative position detection method and ink jet recording device - Google Patents

Abstract

To provide a relative position detection method and an ink jet recording device, which can easily and more accurately detect a positional relation between head modules.SOLUTION: A relative position detection method of a head module 210 includes: a recording operation step for discharging ink from predetermined nozzles in a plurality of head modules and recording prescribed test images related to identification of impact positions of ink from the nozzles; a capturing step for causing a capturing sensor 41 to capture the test images while scanning the capturing sensor in a width direction; and a specifying step for identifying the positional relation between the impact positions from the capturing result and specifying the relative positions of the plurality of head modules. In the specifying step, the positional relation between the impact positions is identified within a limited width in which the capturing sensor moves for a prescribed time less than a half period of speed fluctuation components generated in scanning speed of the capturing sensor.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a relative position detection method and an inkjet recording apparatus.

  2. Description of the Related Art There is an inkjet recording apparatus that records an image or the like on a medium by discharging ink from a nozzle and causing the ink to land on a desired position on the medium. In the inkjet recording apparatus, a plurality of head modules including one or more recording heads in which a plurality of nozzles are arranged are arranged, and a line head is used in which the nozzles are arranged over the entire width in the predetermined width direction of the recording medium. The ink can be landed at high speed in a predetermined two-dimensional surface on the medium while the medium is moved in the transport direction intersecting the width direction.

  In addition, there is a technique of imaging a predetermined recording content and detecting a defect of the recording content. The inkjet recording apparatus includes a reading unit that performs imaging and reads the recorded content, and performs imaging of a necessary range by relatively moving an imaging range of the reading unit with respect to the recorded content. Then, when a problem is detected in the imaging result, various operations are performed to correct and adjust the detected problem, or a user of the inkjet recording apparatus is notified of the occurrence of the problem. The problems include defective ink ejection from the nozzles, relative displacement of the ink ejection amount from each nozzle, and relative positional deviation of each head module.

  At this time, if an imaging unit in which imaging elements are arranged corresponding to the width of the line head is provided and the recording content is moved with respect to the imaging unit, the number of imaging elements, size and weight increase, and calibration is performed. Leading to an increase in the number of tasks, an increase in support structure, and an increase in cost. On the other hand, by reducing the number of imaging elements and moving the imaging unit relative to the recorded content to perform imaging and reading, downsizing of the configuration and cost reduction can be achieved (for example, Patent Documents 1 and 2). ).

JP, 2013-71289, A Unexamined-Japanese-Patent No. 2006-35727

  Among the problems that occur in the detection target image, for those that require information on the imaging position (pixel position) of each imaging element, such as relative positional deviation between head modules, when moving the imaging element relative to the recording content, movement It is necessary to accurately specify the imaging position by the imaging element in the inside. However, in response to such a movement operation, a minute vibration is easily generated in the reading unit and its supporting member, and the vibration of the imaging position is generated by the vibration. In order to effectively reduce such vibrations and pinpoint the position accurately, the structural condition of the support member and the accuracy condition of the shape of each part become severe, and in the end, it does not lead to a reduction in size and cost as a whole. There is a problem of becoming

  An object of the present invention is to provide a relative position detection method and an ink jet recording apparatus capable of easily detecting the positional relationship between head modules more accurately.

In order to achieve the above object, the invention according to claim 1 is
A method of detecting the relative position of a head module in a line head in which a plurality of head modules in which a plurality of nozzles are arranged at mutually different positions in a predetermined width direction is arranged,
A recording operation step of ejecting ink from predetermined nozzles in a plurality of head modules and recording a predetermined test image related to identification of the landing position of the ink from the nozzles;
An imaging step of imaging the recorded test image while scanning an imaging unit for imaging the landing surface of the ink in the width direction;
Identifying the positional relationship of the impact positions from the imaging result of the test image, and identifying the relative positions of the plurality of head modules based on the positional relationship;
In the identifying step, the plurality of heads of which the relative position is to be identified within a limited range in which the imaging unit moves within a predetermined time less than a half period of a speed fluctuation component generated in the scanning speed of the imaging unit in the imaging step. The module is characterized in that the positional relationship of the impact positions is identified.

The invention according to claim 2 is the relative position detection method according to claim 1.
In the specifying step, the limited width is determined such that a difference between the velocity fluctuation components within the limited width is equal to or less than half of an amplitude of the velocity fluctuation component.

The invention according to claim 3 is the relative position detection method according to claim 1.
The predetermined time may be set to 1/10 or less of the speed fluctuation component.

The invention according to claim 4 is the relative position detection method according to any one of claims 1 to 3.
The half cycle is characterized in that it is determined according to the one of the maximum frequency among the speed fluctuation components above a predetermined reference strength.

The invention according to claim 5 is the relative position detection method according to any one of claims 1 to 4,
In the recording operation step, the test image is recorded within the limited width.

The invention according to claim 6 is the relative position detection method according to any one of claims 1 to 5,
When the relative positions of the plurality of head modules are specified at two or more locations, in the specifying step, the positional relationship of the landing positions within the limited width is identified for each of the two or more locations. Do.

The invention according to claim 7 is the relative position detection method according to any one of claims 1 to 6,
The plurality of head modules have two or more recording heads arranged in a predetermined positional relationship,
In the specifying step, the relative positions of the plurality of head modules are specified to thereby specify the relative positions of the recording heads included in the plurality of head modules.

The invention according to claim 8 is the relative position detection method according to any one of claims 1 to 7,
In the recording operation step, the test image including the predetermined mark is recorded by each of the two head modules adjacent in the width direction,
In the identifying step, the relative position of the two adjacent head modules is identified according to the positional relationship within the limited width of the marker.

The invention according to claim 9 is the relative position detection method according to claim 8.
In the recording operation step, the two adjacent head modules eject ink from two or more predetermined numbers of nozzles arranged in a continuous arrangement in the width direction, and each single mark is limited It is characterized in that it is recorded within the width.

In the invention according to claim 10, in the relative position detection method according to claim 8 or 9,
In the recording operation step, a plurality of the marks may be recorded by the two adjacent head modules.

The invention according to claim 11 is the relative position detection method according to claim 10.
The identifying step is characterized in that among the plurality of markers, those whose width in the width direction is out of a predetermined range are not used for specifying the relative position of the head module.

The invention according to claim 12 is the relative position detection method according to claim 10 or 11,
In the specifying step, among the plurality of markers, one having an interval between the adjacent markers which is not within a predetermined reference range is not used for specifying the relative position of the head module.

The invention according to claim 13 is the relative position detection method according to any one of claims 1 to 12:
The line head is plural,
In the recording operation step, the test image is recorded within the limited width by the head modules of the plurality of line heads.
In the identification step, relative positions among the plurality of line heads are identified based on a relative position of the head module having the test image recorded thereon.

The invention according to claim 14 is the relative position detection method according to claim 13.
The plurality of line heads eject ink having spectral characteristics different at least in part from the predetermined line head from the plurality of nozzles.
In the imaging step, the imaging unit can capture the test image by at least one of a plurality of spectral sensitivity characteristics,
In the identifying step, the positional relationship of the landing positions is identified using one of imaging results of the test image obtained by spectral sensitivity characteristics respectively determined according to the spectral characteristics of the ink.

The invention according to claim 15 is
A line head in which a plurality of head modules in which a plurality of nozzles are arranged at mutually different positions in a predetermined width direction are arranged;
A scanning operation unit configured to scan an imaging unit for imaging an ink landing surface in the width direction;
A recording control unit that ejects ink from a predetermined nozzle in the head module and records a predetermined test image related to identification of the landing position of the ink from the nozzle;
An imaging control unit that causes the imaging unit to perform imaging while causing the scanning operation unit to scan the imaging unit;
An identification unit that identifies the positional relationship of the landing positions from the imaging result of the test image, and identifies relative positions of the plurality of head modules based on the positional relationship;
Equipped with
The identification unit is a target for identifying a relative position within a limited range in which the imaging unit moves in a predetermined time less than a half cycle of a velocity fluctuation component generated in a scanning speed of the imaging unit when scanning the imaging unit. It is an inkjet recording apparatus characterized by identifying the positional relationship of the landing positions for a plurality of head modules.

  According to the present invention, there is an effect that the positional relationship between the head modules can be easily detected more accurately.

FIG. 1 is an overall perspective view of an inkjet recording apparatus. It is a bottom view which shows the conveyance side and the field corresponding to in a head unit. FIG. 2 is a block diagram showing a functional configuration of the inkjet recording apparatus. It is a figure which shows the example of the imaging position shift according to the blurring of scanning speed. It is a figure which shows the example of the test image which concerns on the position adjustment between head modules. It is a flowchart which shows the control procedure of a module position identification process. It is a figure which shows the example of the recording defect of a marker.

Hereinafter, embodiments of the present invention will be described based on the drawings.
FIG. 1 is an overall perspective view of an inkjet recording apparatus 100 according to an embodiment of the present invention.

  The inkjet recording apparatus 100 has a plurality of, in this case, eight line heads, and can eject a single-pass ink to perform recording of a color image. An image recording unit 20, an ink supply unit 30, a reading unit 40, and the like are provided.

  The conveyance unit 10 includes a drive roller 11, a conveyance drive unit 12, a conveyance belt 14, and the like. The conveyance drive unit 12 includes a rotation motor that causes the drive roller 11 to rotate at a predetermined speed. An endless transport belt 14 is wound around the drive roller 11 together with a driven roller (not shown), and the transport belt 14 is circularly moved by the rotation of the drive roller 11. The recording medium is placed on the conveyance surface with the outer surface of the conveyance belt 14 as the conveyance surface, and the recording medium is conveyed in the conveyance direction as the conveyance belt 14 circulates.

  The image recording unit 20 includes a carriage 22, a carriage lifting unit 23, etc. The combination of the carriage 22 and the carriage lifting unit 23 corresponds to the number of ink colors (the number of patterns of spectral characteristics) (a plurality, here) Eight sets) are provided. The carriages 22 respectively extend in the direction intersecting the conveyance direction of the recording medium by the conveyance unit 10, here, in the width direction orthogonal to the direction, and are disposed above (height direction) the conveyance surface of the recording medium by the conveyance unit 10. It is done. Head units 21 (see FIG. 2; line heads) are fixed to the carriages 22 so that ink droplets can be ejected from the openings of the nozzles across the entire width of the recording medium to be conveyed. The number of nozzles included in each of the eight (plural) head units 21 is appropriately determined according to the recording resolution, the size of the recording medium which can be recorded by the inkjet recording apparatus 100, and the like. The plurality of carriages 22 are provided at mutually different positions in the transport direction. The carriage 22 is provided so that the position in the height direction can be changed by the carriage elevating unit 23, and the distance from the transport surface of the head unit 21 is also changed as the carriage 22 moves.

The carriage elevating unit 23 changes the distance from the transport surface of the carriage 22. The carriage lifting unit 23 includes a lifting motor 232, an electromagnetic brake 233, a beam member 234, a support portion 235, and the like.
Two beam members 234 are provided substantially in parallel in the direction (here, the direction orthogonal to the transport direction, that is, the width direction) intersecting the transport direction on the upper portion of the transport belt 14 (side of the transport surface of the recording medium). Support portions 235 are fixed to both ends of the support. A lift motor 232, an electromagnetic brake 233 and a carriage 22 are attached to the support portion 235.
The carriage 22 is moved up and down according to the operation of the lift motor 232 and the electromagnetic brake 233 driven based on the control signal from the control unit 50 (see FIG. 3), and the position is determined.

  The elevation motor 232 moves the carriage 22 at a predetermined elevation speed. As the elevation motor 232, for example, a servomotor or a stepping motor is used.

  The electromagnetic brake 233 maintains the fixed state of the carriage 22. When the fixed state is released according to the drive signal, the movement of the carriage 22 by the lift motor 232 is temporarily enabled. That is, in the normal state including the time of power supply disconnection, the electromagnetic brake 233 fixes the carriage 22. For example, a disc brake is used as the electromagnetic brake 233.

  The ink supply unit 30 stores ink of each color used for image recording and supplies the ink to the head unit 21. Here, the ink storage tank 31 of each color is disposed in a dedicated rack 32 and connected to a head unit 21 that discharges the ink of each color through a pipe such as a tube. The ink of each color is not particularly limited, but here, there are eight different colors, including C (cyan), M (magenta), Y (yellow) and K (black), and here, further, The inks of P (pink), S (sky), G (gray) and O (orange) can be respectively supplied. The ink of each color is ejected as fine dots by the nozzles of each head unit 21 supplied, and lands on the recording medium, and is expressed by the density according to the number of fine dots, the size of the dots (droplet amount), etc. The mixed color image is recorded. The color of the ink stored in the ink storage tank 31 and supplied to the head unit 21 may be replaceable.

  The reading unit 40 is provided on the downstream side with respect to the conveyance direction of the image recording unit 20, and images and reads the surface of the recording medium on which the image is recorded by the image recording unit 20. The reading unit 40 includes an imaging sensor 41 (imaging unit), a scanning unit 42 (scanning operation unit), and the like.

  The imaging sensor 41 has a plurality of imaging elements arranged at least in the transport direction, and can be imaged across the entire width of the recording medium (ink landing surface of ink) by being moved in the width direction (scanning direction) by the scan drive unit 45 It has become. As an imaging element, a CCD sensor, a CMOS sensor, etc. are used. Here, the imaging sensor 41 can capture an image in each wavelength band of RGB three colors, and reads a color image.

  The scanning unit 42 moves (scans) the imaging sensor 41 in the width direction. Here, the scanning unit 42 fixes the imaging sensor 41 to a base (supporting member), and moves the base in the width direction (scanning direction) of the base. The scanning drive unit 45 is not particularly limited, but for example, a belt fixed to a base and a motor for moving the belt are used. Moreover, the rail etc. which a base can move in parallel may be provided.

FIG. 2 is a bottom view showing the surface of the head unit 21 corresponding to the transport surface.
Here, since the head units 21 of each color have the same shape and configuration, any one of them will be described.

  As shown in FIG. 2A, 16 recording heads 211 are fixed to the head unit 21. On the bottom surface of each recording head 211, four rows of nozzle arrays in which a plurality of nozzle openings 27a are arrayed in the width direction are provided in the transport direction. The number and the arrangement of the nozzle openings 27a shown here are examples for explanation and may be arbitrarily determined. The positions of the nozzle openings 27a in each row are determined so as to be at predetermined intervals (twice the nozzle pitch) in the width direction.

  Sixteen recording heads 211 included in one head unit 21 form eight (plural) head modules 210 in pairs of two. The two recording heads 211 forming a pair are provided adjacent to each other in the transport direction. Further, as shown in the enlarged view of FIG. 2B, these two recording heads 211 differ in the width direction by the nozzle pitch so that the respective nozzle openings 27a (nozzles) are alternately positioned in the width direction. It is arranged at the position, that is, in the positional relationship specified in advance. That is, in each head module 210, the plurality of nozzles are arranged at positions different from each other in the nozzle pitch in the width direction over the printable width. The dot diameter (diameter) on the recording medium after the ink ejected from the nozzle openings 27a provided at adjacent positions in the width direction lands on the recording medium is larger than the nozzle pitch. Therefore, the inks ejected from the adjacent nozzles in the width direction partially overlap and connect on the recording medium. As a result, line segments L1 and L2 (markers) each having a thickness corresponding to the number of the nozzles are formed by the ink ejected from the plurality of adjacent nozzles.

  Similarly, the conveyance speed of the recording medium by the conveyance drive unit 12 during the normal image recording operation is such that the conveyance distance between the ink discharge intervals from the nozzles is smaller than the dot diameter of the ink landed on the recording medium. Thus, the ink ejected continuously from the same nozzle 27 at the ink ejection interval is partially overlapped and connected on the recording medium. That is, the ink ejected continuously from the plurality of nozzles adjacent in the width direction has a line width corresponding to the number of the plurality of nozzles and a line length corresponding to the number of times of continuous ejection on the recording medium. .

  The head modules 210 adjacent to each other in the width direction are alternately arranged in the transport direction. That is, the plurality of head modules 210 are provided in a staggered manner in the head unit 21. The arrangement range of the nozzle openings 27a in each head module 210 is arranged with the arrangement range of the nozzle openings 27a in the other head modules 210 adjacent to each other in the width direction and a slight overlapping range in the width direction. In the image recording operation, in the overlapping range, the ink may be ejected only from the nozzles provided in one of the head modules 210 for each position in the width direction. Alternatively, one of the two nozzles at the same position in the width direction in both head modules 210 may be selected and ejected at a predetermined ratio for each position in the transport direction. Various well-known selection algorithms can be used.

  FIG. 3 is a block diagram showing the functional configuration of the inkjet recording apparatus 100 of the present embodiment.

  The inkjet recording apparatus 100 controls the carriage drive unit 24, the head drive unit 25, the nozzles 27, the liquid transfer drive unit 35, the scan drive unit 45, in addition to the transport drive unit 12 and the imaging sensor 41 described above. The control unit 50 includes a unit 50 (recording control unit, imaging control unit, specifying unit), a storage unit 60, a communication unit 70, a display / operation receiving unit 80, a bus 90, and the like.

  The carriage drive unit 24 outputs a drive signal to the electromagnetic brake 233 and the lift motor 232 according to the control signal from the control unit 50 to loosen the electromagnetic brake 233 and operate the lift motor 232 to move the carriage to a desired position. Or stop the lift motor 232 and fix the carriage by the electromagnetic brake 233.

  The head drive unit 25 outputs a drive signal that causes pressure fluctuation in the ink in the ink flow path communicating with each nozzle 27 of the head module 210 based on the control of the control unit 50. For example, a piezoelectric element is used to generate pressure fluctuation, and the ink flow path, in particular, a size for appropriately causing pressure fluctuation, is generated by causing deformation according to an applied voltage, that is, a drive signal voltage. And deform the pressure chamber which is defined and formed. As the drive signal, one or a plurality of voltage waveform patterns are determined in advance, and in accordance with the control signal from the control unit 50 and the image data, the drive with the voltage waveform pattern is performed on the piezoelectric element corresponding to each nozzle. The presence or absence of signal output is determined. The ink pushed out from the nozzle opening 27a by the drive signal is separated from the ink in the ink flow path by an appropriate amount and discharged as an ink droplet.

  The liquid transfer drive unit 35 has a liquid transfer pump that transfers the ink from the ink storage tank 31 to each head module 210.

  The scan drive unit 45 drives a motor or the like that moves the imaging sensor 41 in the width direction as described above.

  The control unit 50 generally controls the overall operation of the inkjet recording apparatus 100. The control unit 50 includes a CPU 51 (Central Processing Unit), a RAM 52 (Random Access Memory), and the like.

  The CPU 51 performs various arithmetic processing, and controls conveyance of a recording medium in the inkjet recording apparatus 100, supply of ink, ejection of ink, reading operation of a recorded image, and the like. In addition, the CPU 51 performs various processes related to image recording based on image data, status signals of respective units, clock signals, and the like according to a program read from the storage unit 60.

  The RAM 52 provides the CPU 51 with a working memory space, and stores temporary data. The storage area of temporary data may be appropriately shared with the DRAM area of storage unit 60.

  The storage unit 60 stores control programs, various setting data, and job data relating to an image recording operation, that is, image data to be recorded, processing data thereof, information relating to operation settings, and the like. The control program includes a program 61 used for various adjustments such as a program for identifying an ejection failure nozzle causing an ink ejection failure, and a detection program for detecting positional deviation between printing heads. The setting data includes an ejection failure nozzle list 62 indicating the position of a nozzle (ejection failure nozzle) causing an ink ejection failure, and limited width information 63 related to the later described limited width. The limited width information 63 may be the value of the limited width itself, or may be test image data which is predetermined according to the limited width, or the reading range setting thereof. The setting data includes each head unit 21, the type of ink ejected from the head unit 21, and a wavelength band appropriate for imaging with respect to the type of ink (spectral sensitivity characteristic, that is, RGB here). And ink information 64 in association with any information.

  The storage unit 60 here includes a DRAM and a non-volatile memory. Temporary storage data such as job data and processing data may be stored in the DRAM for high-speed processing, and may be erased after the image recording operation is completed. The program and setting data are held by the non-volatile memory, and these data are held even when the power supply to the inkjet recording apparatus 100 is interrupted. Among the data stored in the non-volatile memory, for example, initial data and a core program may be stored in a non-erasable rewritable ROM or the like.

  The communication unit 70 is a communication interface that controls communication operation with an external device. The communication interface includes, for example, one or more network cards compatible with various communication protocols such as a LAN card. The communication unit 70 acquires job data including image data to be recorded and settings relating to image recording from an external device based on the control of the control unit 50, and transmits status information and the like to the external device. it can.

  The display / operation reception unit 80 displays the status of the inkjet recording apparatus 100, an operation menu, and the like according to a control signal from the control unit 50, and receives a user operation and outputs the operation to the control unit 50. The display / operation reception unit 80 has, for example, a touch sensor or the like as the operation reception unit, and also has a display screen such as a liquid crystal screen provided so as to overlap with the touch sensor. The control unit 50 causes the display screen to display various menus and the like for receiving an instruction by the status and the touch sensor. The control unit 50 associates the information of the contents and the position of the displayed menu with the information of the type and the position of the touch operation of the user accepted by the touch sensor, and processes the processing according to the operation. Perform control operations to be performed by each part of In addition, an LED lamp, a push button switch, a numeric keypad, or the like may be provided as the display / operation reception unit.

  The bus 90 is a path that electrically connects the control unit 50 and the components that exchange signals with the control unit 50, and transmits the signal.

Next, the operation of the reading unit 40 of the present embodiment will be described.
As described above, in the imaging sensor 41, imaging elements are arrayed along the transport direction so as to enable imaging with a predetermined width, and the imaging sensor 41 is scanned by the scan drive unit 45 in the transport direction of the recording medium (that is, the scanning direction). By performing an imaging operation while being scanned and moved, an image in a reading range corresponding to the arrangement range of the imaging elements and the scanning distance is read from the recording medium.

  At this time, the scan drive unit 45 tries to move the imaging sensor 41 at a predetermined constant speed, but in actuality, depending on the support strength, the shape of each part such as a motor, and the accuracy of operation, etc. Shake (speed fluctuation component) occurs. Such blurring in speed leads to a shift in imaging position in the width direction (scanning direction) by each imaging element.

FIG. 4 is a view showing an example of the imaging position deviation according to the blurring of the scanning speed.
The imaging position shift according to the velocity fluctuation has a period of movement time or more of the width of each head module 210 (here, for example, a width of 2048 nozzles at a nozzle pitch of 720 dpi, ie, about 72.2 mm). The thing and the thing of the period shorter than this are mixed. Among these, it is possible to obtain a correction amount in advance for the shift of the imaging position with respect to the constant offset value and the long-period fluctuation about the time required for the movement of the scanning distance.

  On the other hand, vibration of a short cycle relative to the time required for moving the scanning distance, here, the time required for scanning a distance of about 1⁄5 of the width of the head module 210 mainly, in each pixel of the imaging data An imaging position deviation larger than the size (width) may occur. The cycle of such vibration is determined by the stepping operation cycle of the motor, the accuracy of the eccentricity or distortion of the motor, roller or belt shape, or the resonance frequency determined according to the weight and size of the imaging sensor 41 and the scanning unit 42, etc. The reading unit 40 is uniquely determined. However, such a vibration does not necessarily have a fixed phase and is a combination of vibrations of a plurality of cycles, so that it is difficult to perform correction in advance.

  In the inkjet recording apparatus 100 according to the present embodiment, the width for recording a test image for which position information is required is limited to the distance that the imaging unit moves in a predetermined time less than the half cycle of the vibration. That is, by recording the test image in the range less than the amplitude of the imaging position deviation caused by these vibrations, the change in the relative magnitude of the identified head position deviation is reduced. Therefore, if limited to a shorter width, the change in relative magnitude of head misalignment can be made smaller.

  The vibration may include multiple cycles as described above. In the inkjet recording apparatus 100, among the frequencies (velocity fluctuation components) whose vibration intensity obtained by spectrum analysis is equal to or higher than a predetermined reference intensity, the 1/10 period is predetermined with reference to the maximum frequency (shortest period). By recording a test image of a width (limited width) corresponding to the movement distance of the imaging sensor 41 by scanning for this predetermined time as time, a change in relative magnitude of imaging position deviation is not more than half the amplitude, for example Reduce to about 1/5. As a result, the imaging positional deviation amount is reduced to about 0.4 pixels at the maximum, and the positional deviation amount between the head modules 210 specified is sufficiently accurate to the extent that the influence of the head positional deviation in the recorded image is inconspicuous The positional deviation of each head module 210 can be adjusted.

  The oscillation period is pre-tested and identified. An image whose position on the recording medium can be specified (for example, the position (coordinates) on the recording medium in the transport direction is proportional to the position (coordinates) on the recording medium in the width direction. Image is not required to be read by the imaging sensor 41 scanned in advance, and the relationship between the elapsed time and the reading position at each time is acquired, whereby a change in the value of the imaging position blurring with respect to time is identified. . Alternatively, the position change of the imaging sensor 41 to be scanned may be detected more directly by another fixed sensor or the like. By analyzing these results spectrally, the intensity of vibration at each frequency can be obtained.

  By identifying the maximum frequency (shortest period) among the obtained vibration strengths at each frequency and among those higher than a predetermined reference strength, a test image (described later) is determined according to the specified frequency and the transport speed. The maximum value of the width of the inter-head alignment image) is determined. As described above, the limited width may be defined so as to more appropriately suppress the imaging position deviation within the range below this maximum value.

  Instead of setting the limited width based on the predetermined time with reference to the maximum frequency, the limited width itself is adjusted, and the difference of the value of the imaging position blur due to the speed fluctuation component within the limited width is a predetermined value, for example, It may be determined to be half or less of the amplitude. As described above, since the vibration of each superimposed frequency may change in phase or the like, the limited width can be determined with a margin so that the amplitude is sufficiently smaller in any superposition. The frequency that is equal to or higher than the reference intensity often stands as a narrow peak, so in this case, the difference in the limited width is half or less than the predetermined value with respect to the sum of the amplitudes at the respective frequencies. As such, the limited width may be determined.

FIG. 5 is a view showing an example of a test image related to the position adjustment between the head modules 210. As shown in FIG.
As described above, the arrangement of the nozzle openings 27a on the adjacent sides of the two head modules 210 adjacent in the width direction is connected with a slight overlap in the width direction. In the test image (inter-head alignment adjustment image for identifying the impact position of the ink), the ink is ejected from the predetermined nozzles of the end portion (seam area) of each head module 210 including the overlapping portion to record Marker (label) is included. By imaging this head-to-head alignment adjustment image and identifying the positions of the markers on the image of the imaging result, that is, the impact positions of the ink, the impact positions of the two head modules 210 that are targets for specifying relative positions. The positional relationship in the width direction is obtained. Then, based on this positional relationship (that is, the positional relationship of the markers), the distance between the predetermined reference positions of the two head modules 210 (relative position; predetermined reference positions of the recording heads 211 provided in the head module 210 (Also relative position) is identified. Further, by detecting this distance and the deviation from the designed distance between the reference positions in the width direction, the adjustment amount of the positional deviation of the head module 210 can be obtained. Here, as shown in FIG. 5A, an inter-head position adjustment image is recorded corresponding to seven locations that are joints of eight head modules 210.

  Here, each marker is recorded as a single line (mark) of a predetermined length by ink ejected from four (a predetermined number or more of two or more) nozzles whose arrangement order is continuous in the width direction in the head module 210. Ru. For each head module 210, a plurality of such single lines are recorded at predetermined intervals, here, at a 16-nozzle interval.

At this time, the nozzles for discharging the ink are determined such that the widths d1 to d7 of the respective inter-head position adjustment images become equal to or less than the above 1/10 cycle. As a result, in each head-to-head position adjustment image, the size of the deviation of the landing position of the ink ejected from each nozzle does not change significantly. That is, as long as the relative position of the deviation amount of the landing position is discussed, the error of the relative position is kept within a sufficiently small range. As a result, the relative displacement amounts of the landing positions from the nozzles of the two head modules 210 can be accurately determined at seven locations. Since the width of each head module 210 is constant, by adding the deviation amount with reference to the position of one head module 210, the relative position from the design position of the other head module 210 to the one head module 210 is obtained. All misalignment amounts can be identified.
If the head module 210 has a shift or inclination in the transport direction, a shift in the imaging position occurs in the direction of the array width of the imaging elements regardless of the scanning speed, so obtain the shift amount of the imaging position Correction can be performed as usual.

  In addition to alignment between the plurality of head modules 210 in each head unit 21, alignment of all the head modules 210 among the plurality of head units 21 can be performed. As shown in FIG. 5B, eight inter-head position adjustment images at seven joints in each of the eight head units 21 can be arranged and recorded as eight inter-head position adjustment images in the transport direction. In this case, for example, a head module 210 that ejects ink of another color (MYKPSGO, mutually different colors) with reference to the head module 210 of the head unit 21 that ejects C color ink that is closest to the initial position of the imaging sensor 41 The relative position (also relative position between the head units 21) of the head modules 210 of the unit 21 can be specified.

  At this time, each length in the conveyance direction of the inter-head position adjustment image is set so that the array width in the conveyance direction of the imaging element is longer than the length in the conveyance direction of the inter-head position adjustment image of eight colors. (A predetermined length of the marker) is determined. Thus, the entire inter-head position adjustment image is read by the imaging sensor 41 in a single scan.

FIG. 6 is a flowchart showing a control procedure by the control unit 50 of the module position specifying process executed by the inkjet recording apparatus 100 of the present embodiment.
This module position specifying process is an example of an embodiment of the relative position detection method of the present invention, and is displayed, for example, when installing the inkjet recording apparatus 100 or when replacing the recording head 211, the head module 210, and the head unit 21. -It is started according to the predetermined operation which the operation reception part 80 received.

When the module position identification process is started, the control unit 50 (CPU 51) outputs a control signal to the conveyance drive unit 12 and the head drive unit 25, and an inter-head position adjustment image of each ink color on the recording medium to be conveyed (A predetermined test image relating to the identification of the impact position) is output (step S101; recording operation step). As described above, each head-to-head position adjustment image is provided at each joint area between head modules 210 (at a position where two or more relative positions are specified) (ie, here, 56 positions of 7 × 8 colors). In this case, the recording is performed within a limited width set in a total of 112 pieces, two for each of the two head modules 210. The control unit 50 outputs a control signal to the scan drive unit 45 and the imaging sensor 41, and causes the imaging sensor 41 to scan the head-to-head alignment adjustment image while scanning in the width direction at a predetermined scanning speed ( Step S102; imaging step). At this time, the control unit 50 may cause the conveyance drive unit 12 to stop the conveyance operation of the recording medium. The front-rear relationship between the start timing of the imaging operation and the movement start timing of the imaging sensor 41 related to scanning is not limited as long as the inter-head position adjustment image can be appropriately captured. As described above, even if the control unit 50 performs scan control at a constant scan speed, a speed fluctuation component is actually generated in the scan speed.
Further, when the imaging sensor 41 can separately perform imaging in a plurality of wavelength bands (spectral sensitivity characteristics) such as RGB, imaging data of each wavelength band may be acquired.

  The control unit 50 sets the color number C to "0" and sets the module number N to "0" as an initial value (step S103). The control unit 50 reads a marker (ink landing position of ink) at the junction of the head module 210 (hereinafter referred to as module (C, N)) of color number C, module number N and module (C, N + 1) The detection position of the marker in the read image is identified from the imaging result (step S104). The detection of the marker may be performed by limiting the area on the read image assumed in advance and simply detecting the area based on the reference density, and the area limited in advance may be separately recorded at the end of the recording medium or the like. It may be corrected based on the detected position of the reference mark not shown. Alternatively, after all markers are detected, markers related to the junction of module (C, N) and module (C, N + 1) may be identified based on the positional relationship of the markers. When there is imaging data of a wavelength band where it is easy to detect a marker depending on the color of the ink, the control unit 50 appropriately selects imaging data (imaging result) of one or more (part or all) wavelength bands. Use to identify the marker detection position.

  The control unit 50 specifies the positional relationship of the detection position of the marker, and based on the positional relationship, the module (C, N + 1) beginning with the position of the module (C, N) (that is, the imaging sensor in the width direction The positional deviation amount (relative position of a plurality of head modules) relative to the design position (design distance) of the position of the nozzle opening 27a closest to the initial position 41 is identified (step S105). Here, for example, the control unit 50 obtains the average position in the width direction, the barycentric position of the density value, and the like for the plurality of markers of each head module 210, and the relative positional deviation amount is determined according to the magnitude of the deviation. Identify

  The control unit 50 calculates the start position of the module (C, N + 1) relative to the module (C, 0) (step S106). The control unit 50 adds the positional deviation amount from the module (C, 1) to the module (C, N + 1) to obtain the integrated positional deviation amount, and designs the position for the module (C, 0) of the module (C, N + 1). The position of the module (C, N + 1) relative to the module (C, 0) is calculated by adding the integrated positional deviation amount to

  The control unit 50 calculates the head position in the width direction of the module (C, N + 1) with respect to the module (0, 0) (step S107). The control unit 50 adds the relative positional deviation amount of the module (C, 0) with respect to the module (0, 0) to the position of the module (C, N + 1) calculated in step S106 to obtain the module (0, 0). Calculate the position of module (C, N + 1) with respect to 0). When the color number C is “0”, the addition process is not performed, and the position of the module (C, N + 1) with respect to the module (C, 0) obtained in step S 106 is used as it is with respect to the module (0, 0). It can be at the position of module (C, N + 1).

  The control unit 50 adds "1" to the module number N (step S108). The control unit 50 determines whether the new module number N is equal to the number N0 of the head modules 210 in the head unit 21 (step S109). If it is determined that the number N0 of the head modules 210 is not equal ("NO" in step S109), the process of the control unit 50 returns to step S104.

If it is determined that the module number N is equal to the number N0 of the head modules 210 (“YES” in step S109), the control unit 50 adds “1” to the color number C, and adds the module number N It is set to "0" (step S110). The control unit 50 determines whether the color number C is equal to the number of colors C0 in the image recording unit 20, that is, the number of head units 21 used for image recording (step S111). If it is determined that they are not equal ("NO" in step S111), the process of the control unit 50 returns to step S104. If it is determined that they are equal ("YES" in step S111), the control unit 50 ends the module position identification process.
The processes of the above-described steps S103 to S111, and at least the processes of steps S104 and S105, constitute a specifying step in the module position specifying process which is the present embodiment of the relative position detection method.

FIG. 7 is a view showing an example of the marker recording failure.
The number of nozzles used for image recording in the ink jet recording apparatus 100 is very large, and often there is a discharge failure such as a decrease in discharge amount or no discharge at all, or an abnormality in the flying direction of the discharged ink. When ejection is not performed from one nozzle, as shown by a line segment Le1 in FIG. 7A, the marker may be split into a plurality of lines, or the line density may decrease when imaging (a single line Instead of a marker, it includes cases where two or more thin (thin) lines are detected at an interval much narrower than the normal interval). Also, if the flight direction of the ink ejected from one nozzle is abnormal, the marker may be divided into a plurality of lines or the impact may be caused by the deviation of the landing position from the normal position as in the line segment Le2. The position may overlap with the ink ejected from the other nozzles to reduce the density, or the width or position of the marker detected by the imaging sensor 41 may be shifted.

  Further, in FIG. 7B, as in the line segment Le3, the nozzles at the end portion of the plurality of nozzles 27 forming the marker can not be discharged, and as in the line segment Le4, the nozzles from the other nozzles 27 are discharged. When the ink is deviated in the overlapping direction with the ink landing position, the thickness of the marker becomes thinner than originally expected. Further, when such a deviation occurs, a deviation also occurs in the distance dLe between the center positions of the respective markers.

  In the process of step S105 described above, among a plurality of detected markers, ones whose line density is lower than the reference, those whose line width is narrower than the reference (outside the predetermined range), and a plurality of adjacent ones If the interval between markers is out of the average value and not within the reference range (parts) etc., it will be excluded when calculating the average value of the position of each marker, and it will be used to specify the relative position of the head module It can not be. In this case, with regard to the excluded markers on both sides, weighting can be performed so that the average position does not shift.

  The ejection failure nozzles already registered in the ejection failure nozzle list 62 can be considered in advance in the module position specifying process. For example, the control unit 50 may select a nozzle that ejects the ink so that the ejection failure nozzle is separated from the nozzle on which the marker is to be formed. In such a case, since the positions of the markers vary, for example, a regression line relating to the detected positions of a plurality of markers may be calculated to obtain a predetermined position on the regression line.

As described above, in the relative position detection method (inter-head position adjustment processing) of the head module 210 in the inkjet recording apparatus 100 according to the present embodiment, the head module in which the plurality of nozzles 27 are arranged at mutually different positions in the predetermined width direction A method of detecting the relative position of the head module 210 in a head unit 21 (line head) in which a plurality of pieces 210 are arranged, wherein ink is ejected from predetermined nozzles 27 in joint areas of the plurality of head modules 210, A recording operation step (step S101) for recording a predetermined inter-head position adjustment image related to the identification of the landing position of the ink from the nozzle 27 and scanning the imaging sensor 41 for imaging the landing surface of the ink in the width direction Capture the recorded image for adjusting the position between heads Imaging step (step S102) for identifying the positional relationship of the landing position from the imaging result of the inter-head position adjustment image, and identifying step for identifying relative positions of the plurality of head modules 210 based on the positional relationship (steps S103 to S111 )including. In the identification step, two adjacent head modules whose relative positions are to be identified within a limited width in which the imaging sensor 41 moves in a predetermined time less than a half period of the speed fluctuation component generated in the scanning speed of the imaging sensor 41 in the imaging step. For 210, the positional relationship of the landing positions is identified.
As described above, even if the imaging position shift due to the vibration occurs in the imaging data, if the relative position is acquired only in the range where the amplitude of the vibration is small, the relative position does not significantly shift, so the accuracy is high. It becomes possible to acquire positional relationship. Therefore, it is possible to efficiently and easily obtain the accurate positional relationship without making a large-scale change such as improving the structure in order to suppress the vibration.

  Further, in the specific step, the limited width is determined such that the difference between the speed fluctuation components within the limited width is equal to or less than half the amplitude of the speed fluctuation component. Since the magnitude of each velocity fluctuation component measured in advance is approximately constant and can change with phase shift, the limited width is determined so that the amplitude is sufficiently smaller than the maximum amplitude. The limited width can be determined with a margin so as to be smaller than the amplitude sufficiently. As a result, the positional relationship of the head module 210 can be acquired efficiently and more surely and accurately.

  Further, the predetermined time for the movement of the limited width of the imaging sensor 41 is set to 1/10 or less of the speed fluctuation component. As a result, the worst case is suppressed to 1/3 or less of the amplitude, and usually, the influence of vibration can be reduced sufficiently. As a result, a shift of several pixels (2 to 3 pixels) can be suppressed to within one pixel, so that a situation in which the position is shifted in pixel units can be prevented.

  Further, the half cycle of the vibration serving as the reference of the determination of the limited width is determined according to the one of the maximum frequency among the speed fluctuation components equal to or higher than the predetermined reference strength. By setting the amplitude of the vibration of the maximum frequency among the vibrations of multiple cycles generated by the combination of the plurality of configurations and factors to a range that can suppress the vibration of the frequency lower than this, the entire vibration is effectively suppressed. can do.

  In the recording operation step, the inter-head position adjustment image is recorded within the limited width. That is, since the inter-head alignment image is not recorded in a portion which is not used for adjusting the relative position of the head module 210, ink can be saved. In addition, it is possible to more easily determine the necessary marker from the imaging data.

  When the relative positions of the plurality of head modules 210 are specified in two or more places, in the specifying step, the positional relationship of the landing positions within the limited width is identified for each of the two or more places. That is, when there are three or more head modules 210, etc., when the both ends are adjacent to another head module 210, it is possible to separately record an inter-head alignment image including the both ends. Thus, the relative position can be specified between all the adjacent head modules 210, and as a result, all the head modules 210 can be properly aligned.

In addition, the plurality of head modules 210 have two or more (here, two) recording heads 211 disposed in a positional relationship specified in advance, and in the identification step, the relative positions of the plurality of head modules 210 are identified By doing this, the relative position of the recording head 211 of the plurality of head modules 210 is specified.
That is, adjustment of the relative position can be performed in units of a plurality of recording heads 211. As a result, the relative position of the recording head 211 where the nozzles 27 are actually provided is appropriately adjusted, and the arrangement of the nozzles 27 becomes appropriate. In particular, even for a line head (head unit 21) that records a high resolution image with a narrow nozzle pitch by combining a plurality of recording heads 211, alignment between the recording heads 211 can be easily performed.

  In the recording operation step, an inter-head position adjustment image including a marker is recorded by each of the two head modules 210 adjacent in the width direction, and in the identification step, the adjacent head is adjusted according to the positional relationship within the limited width of the marker. The relative position of the two head modules 210 is identified. As described above, by specifying the relative positions of the adjacent head modules 210, it is possible to sequentially acquire appropriate positions with respect to the reference head module 210, and therefore, it is possible to obtain all the head modules 210 according to the acquired information. Alignment is easier than identifying an absolute position and does not degrade the image quality.

Further, in the recording operation step, the two head modules 210 adjacent in the width direction eject ink from two or more predetermined numbers of nozzles 27 in which the arrangement order in the width direction is continuous, and each single marker Is recorded within the limited width.
Since the ink ejected from the individual nozzles 27 may have a landing error in itself, it is necessary to specify the position by a marker which continuously connects the ink ejected from the plurality of nozzles 27 on the recording medium. Then, it is possible to more appropriately identify the relative position by reducing the influence of such individual impact position blurring.

  Further, in the recording operation step, a plurality of markers are recorded respectively by two adjacent head modules 210. That is, since a plurality of markers themselves are recorded and the position of the head module 210 is specified based on the positional relationship, the influence of unevenness of the ink landing position from the nozzles 27 and the nozzles 27 having ink discharge failure are further generated. It is possible to more accurately specify the relative position in one process by eliminating the influence of

  In the identification step, among the plurality of markers, those whose width in the width direction is outside the predetermined range are not used to specify the relative position of the head module 210. As described above, when the nozzle 27 that discharges the ink forming the marker includes a discharge failure nozzle and the influence on the identification of the position of the marker becomes a problem, the marker is not used. By identifying the position with the marker of, it is possible to easily prevent the deterioration of the specific position accuracy. In particular, in the case where the positional deviation can not be compensated for even if a single marker is recorded by the ink ejected from the plurality of nozzles 27, the judgment criterion is set so as to be easily detectable. In addition, by arranging a plurality of markers and not using only a part of them, the relative position of the head module 210 can be identified easily and appropriately without having to output the inter-head alignment image again. .

  Further, in the identifying step, among the plurality of markers, those having an interval between adjacent markers which is not within the predetermined reference range are not used to identify the relative position of the head module 210. As described above, when the defective discharge nozzle is included in the nozzle 27 that discharges the ink forming the marker and the influence on the identification of the position of the marker becomes a problem, the marker is not used. By identifying the position with another marker, it is possible to easily prevent the decrease in the accuracy of the specific position.

There are a plurality of head units 21. In the recording operation step, the head-to-head alignment adjustment image is recorded within the limited width by the head modules 210 of the plurality of head units 21. In the specific step, the head-to-head alignment adjustment image is recorded The relative position between the plurality of head units 21 is specified based on the relative position of the head module 210 that has been made.
As described above, not only the relative positions of the plurality of head modules 210 in each head unit 21 but also the relative position between the head units 21 can be specified. Therefore, the relative positional relationship of the nozzles 27 in the entire image recording unit 20 Can be adjusted. Thereby, the positions of the inks of the respective colors can be properly aligned.

  In addition, the plurality of head units 21 eject ink having spectral characteristics different at least in part from other line heads from the plurality of nozzles 27. In step, the imaging sensor 41 adjusts the image for adjusting the position between the heads into RGB wavelength bands The imaging can be performed by at least one of the spectral sensitivity characteristics, and in the specific step, among the imaging results of the inter-head position adjustment image, those obtained with the spectral sensitivity characteristics respectively determined according to the spectral characteristics of the ink are used Identify the positional relationship of landing positions. That is, in the case of using inks of a plurality of colors, etc., since the wavelength band capable of taking a large density gradation differs depending on the ink, the ink impact position is detected and identified using imaging data of the appropriate wavelength band. Thus, the position of the head module 210 can be identified accurately for a wide range of inks. Also, the relative position can be specified stably for different inks regardless of the combination.

Further, in the inkjet recording apparatus 100 according to the present embodiment, the head unit 21 in which a plurality of head modules 210 in which a plurality of nozzles 27 are arranged at mutually different positions in the predetermined width direction is arranged, and imaging of the ink landing surface A scanning unit 42 configured to scan the imaging sensor 41 in the width direction and a control unit 50 are provided. As the recording control unit, the control unit 50 ejects the ink from the predetermined nozzles 27 in the head module 210, and records a predetermined inter-head positional adjustment image related to the identification of the landing position of the ink from the nozzles 27. As an imaging control unit, make the imaging sensor 41 perform imaging while scanning the imaging sensor 41 by the scanning unit 42, identify a positional relationship of landing positions from an imaging result of an inter-head position adjustment image as a identification unit, The relative positions of the plurality of head modules are identified based on the positional relationship. In addition, as the identification unit, the control unit 50 is a relative unit within the limited width in which the imaging sensor 41 moves in a predetermined time less than a half cycle of the speed fluctuation component generated in the scanning speed of the imaging sensor 41 The positional relationship of the impact positions is identified for the plurality of head modules 210 whose position is to be identified.
In such an inkjet recording apparatus 100, the relative position of the head module 210 can be easily adjusted without improving the hardware such as increasing the strength of the configuration related to the attachment or scanning of the imaging sensor 41 or improving the stability. Therefore, it is possible to easily prevent the deterioration of the image quality of the recorded image without increasing the cost or increasing the size of the ink jet recording apparatus 100.

The present invention is not limited to the above embodiment, and various modifications are possible.
For example, in the above embodiment, the positional relationship between the two recording heads 211 included in the head module 210 has been described as being specified in advance. However, the positional relationship of these recording heads 211 may not be specified. In this case, for example, a marker is recorded by the nozzles of each recording head 211 so as to specify the positional relationship between the two recording heads 211 first, and the positional relationship between the recording heads 211 is specified and adjusted. Then, based on the specified positional relationship, processing may be performed to obtain the relative position between the head modules 210 as described above. Alternatively, the relative position between the head modules 210 may be adjusted using only one recording head 211 first, and then the relative position between the recording heads 211 may be adjusted by each head module 210.

  Further, in the above embodiment, although two recording heads 211 are provided in each head module 210, only one recording head may be provided, or three or more recording heads may be provided. Further, the term “head module 210” is defined here for the sake of convenience, and as in the inkjet recording apparatus 100 according to the present embodiment, two recording heads 211 are arranged in a set, and the head unit 21 is collected. Even in the case where they are fixed to each other, each of the recording heads 211 may be treated as the head module 210.

  In the above embodiment, the relative positions of all the head modules 210 in the head units 21 of all the colors with respect to the module (0, 0) are specified. However, the module (C, 0) with respect to the module (0, 0) Only the position of) may be specified, and the position of module (C, N + 1) relative to module (C, 0) may be specified. In particular, when adjusting the relative position of the head module in each head unit 21 after adjusting the position of the head unit 21 based on the relative position of the module (C, 0) with respect to the module (0, 0), Such identification method is effective.

  In the above embodiment, the inter-head position adjustment image is formed within the limited width, but if the range used for specifying the position of the head module 210 is within the limited width, the inter-head position adjustment image itself is It does not have to be within the limited width. For example, an inter-head position adjustment image about twice the limited width is recorded, and the position of the head module 210 is specified using data within the limited width from the ink landing position of the nozzle 27 at the end of the head module 210 You may do it.

  Further, in the above embodiment, although it is assumed that ink of different colors (spectral characteristics) is ejected from the line heads of eight columns, there are some that eject ink of the same color (regardless of the difference of the spectral characteristics). It is also good.

  In the above embodiment, the eight head modules 210 having the nozzle openings 27a arranged in 4 × 2 rows in the width direction are arranged in a staggered pattern, but each head module 210 (recording head 211 The plurality of nozzle openings 27a) are optional as long as they are provided at mutually different positions in the width direction. Also, the plurality of head modules 210 need not be arranged in a staggered manner. For example, the plurality of head modules 210 may be arranged in the width direction at an angle inclined to the width direction at a predetermined angle.

  Further, in the above embodiment, a single linear (line segment) marker is recorded by the ink ejected from the four nozzles 27 in which the arrangement order is continuous in the width direction. However, as shown in FIG. One marker may be recorded with ink ejected from nozzles 27 other than four, such as ink ejection from a single nozzle from the beginning like the line segment Lv1 shown. The shape of the marker may be such that the position in the width direction can be identified at a specific place. Also, the number of markers is not particularly limited. In consideration of the presence of the discharge failure nozzle, the larger number can more accurately and surely specify the position, but may be one.

  Further, in the above embodiment, a constant scanning speed is determined, but it is sufficient that the correspondence between the elapsed time at the time of imaging and the reading position is defined in design. Further, acceleration / deceleration may be performed with a constant acceleration at the start of movement or at the time of stop. Further, the scanning direction (width direction) may be a direction intersecting the arrangement direction of the nozzles and the transport direction.

  Moreover, although the said embodiment mentioned and demonstrated the RGB sensor as an example as the imaging sensor 41, it is not restricted to this. For example, a monochrome visible light sensor may be used as long as it outputs only a monochrome image. Further, the landing positions of the ink may be specified by combining reading results of sensors having plural types of spectral sensitivity characteristics.

Also, in general, the imaging sensor 41 performs imaging with spectral sensitivity characteristics including the respective wavelength bands of RGB, and uses any image corresponding to the ink color (spectral characteristics) to detect a marker and specify a relative position. Although imaging is performed, imaging with a spectral sensitivity characteristic that is not necessary for detection of an ink color marker that is a target for specifying a relative position may not be performed.
In addition, specific details such as the configuration, the shape and the arrangement, the operation content, and the procedure thereof described in the above embodiment can be appropriately changed without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 10 conveyance part 11 drive roller 12 conveyance drive part 14 conveyance belt 20 image recording part 21 head unit 22 carriage 23 carriage raising / lowering part 232 raising / lowering motor 233 electromagnetic brake 234 beam member 235 support part 24 carriage drive part 25 head drive part 27 nozzle 27a nozzle Opening 30 Ink supply unit 31 Ink storage tank 32 Rack 35 Liquid feeding drive unit 40 Reading unit 41 Imaging sensor 42 Scanning unit 45 Scanning unit 50 Control unit 60 Storage unit 61 Program 62 Discharge failure nozzle list 63 Limited width information 64 Ink information 70 Communication unit 80 Display / operation reception unit 90 Bus 100 inkjet recording apparatus 210 head module 211 recording head

Claims (15)

A method of detecting the relative position of a head module in a line head in which a plurality of head modules in which a plurality of nozzles are arranged at mutually different positions in a predetermined width direction is arranged,
A recording operation step of ejecting ink from predetermined nozzles in a plurality of head modules and recording a predetermined test image related to identification of the landing position of the ink from the nozzles;
An imaging step of imaging the recorded test image while scanning an imaging unit for imaging the landing surface of the ink in the width direction;
Identifying the positional relationship of the impact positions from the imaging result of the test image, and identifying the relative positions of the plurality of head modules based on the positional relationship;
In the identifying step, the plurality of heads of which the relative position is to be identified within a limited range in which the imaging unit moves within a predetermined time less than a half period of a speed fluctuation component generated in the scanning speed of the imaging unit in the imaging step. A relative position detection method, comprising: identifying a positional relationship of the impact positions for a module.   The relative position detection method according to claim 1, wherein, in the specifying step, the limited width is determined such that a difference between the velocity fluctuation components within the limited width is equal to or less than half of an amplitude of the velocity fluctuation component. .   The relative position detection method according to claim 1, wherein the predetermined time is set to 1/10 or less of the velocity fluctuation component.   The relative position detection method according to any one of claims 1 to 3, wherein the half cycle is determined according to the maximum frequency among the speed fluctuation components having a predetermined reference intensity or more.   The relative position detection method according to any one of claims 1 to 4, wherein in the recording operation step, the test image is recorded within the limited width. When the relative positions of the plurality of head modules are specified at two or more locations, in the specifying step, the positional relationship of the landing positions within the limited width is identified for each of the two or more locations. The relative position detection method according to any one of claims 1 to 5. The plurality of head modules have two or more recording heads arranged in a predetermined positional relationship,
The relative position of the plurality of head modules is specified in the specifying step, thereby specifying the relative positions of the recording heads included in the plurality of head modules. The relative position detection method described in 4. In the recording operation step, the test image including the predetermined mark is recorded by each of the two head modules adjacent in the width direction,
The relative position of the said two adjacent head modules is specified according to the positional relationship in the said limited width of the said label | marker in the said specific step. The relative as described in any one of the Claims 1-7 characterized by the above-mentioned. Position detection method. In the recording operation step, the two adjacent head modules eject ink from two or more predetermined numbers of nozzles arranged in a continuous arrangement in the width direction, and each single mark is limited The relative position detection method according to claim 8, wherein the relative position is recorded within the width.   10. The relative position detection method according to claim 8, wherein in the recording operation step, a plurality of the marks are recorded respectively by the two adjacent head modules.   11. The relative position according to claim 10, wherein, in the specifying step, one of the plurality of markers whose width in the width direction is outside a predetermined range is not used to specify the relative position of the head module. Detection method.   The identification step is characterized in that among the plurality of markers, those whose distance to the adjacent markers is not within a predetermined reference range are not used to specify the relative position of the head module. Or the relative position detection method of 11 statement. The line head is plural,
In the recording operation step, the test image is recorded within the limited width by the head modules of the plurality of line heads.
The relative position between the plurality of line heads is specified in the identification step based on the relative position of the head module having the test image recorded thereon. Relative position detection method described. The plurality of line heads eject ink having spectral characteristics different at least in part from the predetermined line head from the plurality of nozzles.
In the imaging step, the imaging unit can capture the test image by at least one of a plurality of spectral sensitivity characteristics,
In the identification step, among the imaging results of the test image, the positional relationship of the landing position is identified using one obtained by the spectral sensitivity characteristic determined in accordance with the spectral characteristic of the ink. Item 13. A relative position detection method according to item 13. A line head in which a plurality of head modules in which a plurality of nozzles are arranged at mutually different positions in a predetermined width direction are arranged;
A scanning operation unit configured to scan an imaging unit for imaging an ink landing surface in the width direction;
A recording control unit that ejects ink from a predetermined nozzle in the head module and records a predetermined test image related to identification of the landing position of the ink from the nozzle;
An imaging control unit that causes the imaging unit to perform imaging while causing the scanning operation unit to scan the imaging unit;
An identification unit that identifies the positional relationship of the landing positions from the imaging result of the test image, and identifies relative positions of the plurality of head modules based on the positional relationship;
Equipped with
The identification unit is a target for identifying a relative position within a limited range in which the imaging unit moves in a predetermined time less than a half cycle of a speed fluctuation component generated in a scanning speed of the imaging unit at the time of scanning of the imaging unit. An inkjet recording apparatus, comprising: identifying positional relationships of the landing positions for a plurality of head modules.

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