JP2010042565A - Adjustment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the adjustment accuracy of an adjustment method for a liquid jetting device. <P>SOLUTION: The adjustment method includes steps for: forming a first dot train group comprising a plurality of dot trains arranged at predetermined intervals in a predetermined direction by using a first nozzle train comprising a plurality of nozzles arranged in a predetermined direction; forming a second dot train group comprising a plurality of dot trains arranged at predetermined intervals in a predetermined direction by using a second nozzle train comprising a plurality of nozzles arranged in a predetermined direction at a position where at least a part of the second dot train group overlaps the first dot train group; reading a pattern formed by the first dot train group and the second dot train group by a reading part; performing the frequency analysis of the read image; and adjusting a position of at least one of the first nozzle train and the second nozzle train so that the power spectrum of frequency equivalent to an ideal dot train interval at a part where the first dot train group and the second dot train group overlap each other may be larger after adjustment than before adjustment in a frequency domain. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for adjusting a liquid ejecting apparatus.

A head of a liquid ejecting apparatus (for example, a printer) is provided with a plurality of nozzle rows in which nozzles for ejecting liquid are arranged. These nozzle rows form a large number of dot rows on the medium to print an image. However, for example, if the head position (nozzle row position) and ejection timing are not accurate, the dot row formed on the medium will deviate from the target position. Therefore, it is necessary to adjust the position of the head and the ejection timing.
JP 2005-96368 A

Conventionally, a test pattern is printed using each nozzle row, and adjustment is performed based on the operator visually checking the test pattern.
However, the visual judgment of the worker has a limit in accuracy, and the judgment result may vary depending on the worker. For this reason, there is a possibility that adjustment with high accuracy cannot be performed.
Therefore, an object of the present invention is to improve the accuracy of adjustment.

  A main invention for achieving the above object is to provide a first dot row comprising a plurality of dot rows arranged in a predetermined direction at a predetermined interval using a first nozzle row comprising a plurality of nozzles arranged in a predetermined direction. Forming a group, and using a second nozzle row composed of a plurality of nozzles arranged in the predetermined direction at a position at least partially overlapping the first dot row group, the predetermined direction at the predetermined interval Forming a second dot row group composed of a plurality of dot rows arranged in parallel, reading a pattern formed by the first dot row group and the second dot row group with a reading unit, and a read image In the frequency domain, a power spectrum of a frequency corresponding to an ideal dot row interval in a portion where the first dot row group and the second dot row group overlap in the frequency domain, Seimae as later adjustment is greater than, an adjustment method with, and adjusting at least one position of the second nozzle row and the first nozzle row.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

=== Summary of disclosure ===
At least the following matters will become clear from the description of the present specification and the accompanying drawings.

Forming a first dot row group constituted by a plurality of dot rows arranged in a predetermined direction at a predetermined interval using a first nozzle row constituted by a plurality of nozzles arranged in a predetermined direction; and A second nozzle row constituted by a plurality of nozzles arranged in the predetermined direction at a position at least partially overlapping with the row group, and a second dot row constituted by a plurality of dot rows arranged in the predetermined direction at the predetermined interval. Forming a two-dot row group; reading a pattern formed by the first dot row group and the second dot row group with a reading unit; performing frequency analysis of the read image; The power spectrum of the frequency corresponding to the ideal dot row interval in the overlapping portion of the first dot row group and the second dot row group is larger after the adjustment than before the adjustment. , Adjustment method with, and adjusting at least one position of the second nozzle row and the first nozzle array becomes apparent.
According to such an adjustment method, it is possible to improve the accuracy of adjusting the positional relationship between the first nozzle row and the second nozzle row.

In this adjustment method, when the positional relationship between the first nozzle row and the second nozzle row is adjusted, the first dot row group and the second dot row group overlap in the frequency domain. The power spectrum of the frequency corresponding to the ideal dot row interval in the portion is larger after the adjustment than before the adjustment, and the power spectrum of the frequency corresponding to the predetermined interval is after the adjustment than before the adjustment. It is desirable that at least one position of the first nozzle row and the second nozzle row is adjusted so that is larger.
According to such an adjustment method, the accuracy of adjustment can be further increased.

In this adjustment method, the first nozzle row and the second nozzle row may be provided in the same head, and the tilt of the head may be adjusted.
According to such an adjustment method, the tilt of the head can be adjusted with high accuracy.

In this adjustment method, the head includes a plurality of nozzle rows arranged in a direction intersecting the predetermined direction, and the first nozzle row is a nozzle on one end side in the direction intersecting the predetermined direction. Preferably, the second nozzle row is a nozzle row on the other end side in a direction crossing the predetermined direction.
According to such an adjustment method, it is possible to further increase the accuracy of adjustment of the head tilt.

In this adjustment method, the first nozzle row and the second nozzle row may be provided in separate heads, and the positional relationship of each head in the predetermined direction may be adjusted.
According to such an adjustment method, the positional relationship between the plurality of heads can be adjusted with high accuracy.

In this adjustment method, the positional relationship between the dot rows of the first dot row group and the dot rows of the second dot row group in a non-overlapping portion is obtained, and the adjustment direction is determined based on the result. desirable.
According to such an adjustment method, the adjustment direction can be reliably determined.

Forming a first dot row group composed of a plurality of dot rows arranged in a direction intersecting the predetermined direction at a predetermined interval using a nozzle row composed of a plurality of nozzles arranged in a predetermined direction; A second dot row group composed of a plurality of dot rows arranged in a direction intersecting the predetermined direction at the predetermined interval using the nozzle row at a position at least partially overlapping with the first dot row group. Forming, reading a pattern formed by the first dot row group and the second dot row group with a reading unit, performing frequency analysis of the read image, and in the frequency domain, the first dot The first dot is adjusted so that the power spectrum of the frequency corresponding to the ideal dot row interval in the overlapping portion between the row group and the second dot row group is larger after adjustment than before adjustment. And adjusting the injection timing from the nozzle array when forming a preparative column group the second dot row group,
The adjustment method having
According to such an adjustment method, it is possible to improve the accuracy of adjusting the ejection timing in the nozzle rows that form the dot rows of the first dot row group and the second dot row group.

  Hereinafter, embodiments of the present invention will be described.

=== Overall structure ===
First, an overall configuration of the present embodiment (printing system 100) will be outlined with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of the printing system 100.
As shown in FIG. 1, the printing system 100 according to the present embodiment is a system that includes a printer 1, a computer 110, and a scanner 120.

  The printer 1 is a liquid ejecting apparatus that ejects ink as a liquid onto a medium to form (print) an image on the medium. In the present embodiment, the printer 1 is a color ink jet printer. The printer 1 can print images on a plurality of types of media such as paper, cloth, and film sheets. Details of the configuration of the printer 1 will be described later.

  The computer 110 is a device that controls the printing system 100. The computer 100 includes an interface unit 111, a CPU 112, and a memory 113. The interface unit 111 exchanges data with the printer 1 and the scanner 120. The CPU 112 executes various programs installed in the computer 110. The memory 113 stores the various programs. Among programs installed in the computer 110, there are a printer driver for converting image data output from an application program into print data, and a scanner driver for controlling the scanner 120. The memory 113 stores a program for performing FFT analysis (frequency analysis), and the computer 110 can perform FFT analysis of an image read by the scanner 120 or the like.

  A scanner 120 (corresponding to a reading unit) irradiates light on a document placed on a document table (not shown), and detects reflected light by a sensor (for example, a CCD) (not shown) provided on the reading carriage 121. An apparatus for reading an image of the original. The scanner 120 includes a scanner controller 125 including an interface 122, a CPU 123, and a memory 124, and transmits data indicating an image reading result to the scanner driver of the computer 110 via the interface 122.

<Configuration of Printer 1>
FIG. 2A is a schematic diagram of the printer 1. FIG. 2B is a cross-sectional view of the printer 1. The configuration of the printer 1 will be described below with reference to these drawings and FIG.

  The printer 1 includes a transport unit 20, a carriage unit 30, a head unit 40, a detector group 50, and a controller 60. When the printer 1 receives a print command and print data from the computer 110, the controller 60 controls each unit (conveyance unit 20, carriage unit 30, head unit 40). The printer 1 prints an image on a medium (for example, paper S) based on the print data received from the computer 110. The situation in the printer 1 is monitored by a detector group 50, and the detector group 50 outputs a detection result to the controller 60. The controller 60 controls each unit based on the detection result output from the detector group 50.

  The transport unit 20 is for transporting the paper S in a predetermined direction. Hereinafter, this predetermined direction is referred to as a conveyance direction (also referred to as a sub-scanning direction). The transport unit 20 includes a paper feed roller 21, a transport motor 22 (also referred to as a PF motor), a transport roller 23, a platen 24, and a paper discharge roller 25. The paper feed roller 21 is a roller for feeding the paper S inserted into the paper insertion slot into the printer. The transport roller 23 is a roller that transports the paper S fed by the paper feed roller 21 to a printable area, and is driven by the transport motor 22. The platen 24 supports the paper S being printed. The paper discharge roller 25 is a roller for discharging the paper S to the outside of the printer, and is provided on the downstream side in the transport direction with respect to the printable area. The paper discharge roller 25 rotates in synchronization with the transport roller 23.

  When the transport roller 23 transports the paper S, the paper S is sandwiched between the transport roller 23 and the driven roller 26. Thereby, the posture of the paper S is stabilized. On the other hand, when the paper discharge roller 25 transports the paper S, the paper S is sandwiched between the paper discharge roller 25 and the driven roller 27.

  The carriage unit 30 is for moving the head in a direction crossing the transport direction. Hereinafter, a direction intersecting with the transport direction is referred to as a moving direction (also referred to as a main scanning direction). The carriage unit 30 includes a carriage 31 and a carriage motor 32 (also referred to as a CR motor). The carriage 31 can reciprocate in the moving direction and is driven by a carriage motor 32. Further, the carriage 31 detachably holds an ink cartridge that stores ink.

  The head unit 40 is for ejecting ink onto the paper S and has two heads. A plurality of nozzles for ejecting ink are provided on the lower surface of each head. Details of the head unit 40 will be described later.

  The detector group 50 includes a linear encoder 51, a rotary encoder 52, a paper detection sensor 53, an optical sensor 54, and the like. The linear encoder 51 detects the position of the carriage 31 in the moving direction. The rotary encoder 52 detects the rotation amount of the transport roller 23. The paper detection sensor 53 detects the position of the leading edge of the paper S being fed. The optical sensor 54 detects the presence or absence of the paper S by a light emitting unit and a light receiving unit attached to the carriage 31. The optical sensor 54 can detect the position of the edge of the paper S while being moved by the carriage 31 to detect the width of the paper S. The optical sensor 54 can also detect the front end (end on the downstream side in the transport direction) and the rear end (end on the upstream side in the transport direction) of the paper S depending on the situation.

  The controller 60 is a control unit for controlling the printer 1. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64. The interface unit 61 transmits and receives data between the computer 110 which is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and includes storage elements such as a RAM and an EEPROM. The CPU 62 controls each unit via the unit control circuit 64 in accordance with a program stored in the memory 63.

<About the configuration of the head unit>
FIG. 3 is an explanatory diagram of the configuration of the head unit 40. Here, the head unit 40 is seen from the top of the printer 1. The head unit 40 of the present embodiment has two heads (a first head 410 and a second head 420).

  The first head 410 and the second head 420 are provided side by side in the movement direction. Each head has a plurality of nozzle rows in which a plurality (n) of nozzles are arranged at a nozzle pitch D in the transport direction (predetermined direction). In the case of FIG. 3, each head has four nozzle rows (from the left side, a magenta (M) ink nozzle row, a yellow (Y) ink nozzle row, a cyan (C) ink nozzle row, and a black (K) ink nozzle row). is doing. In addition, the nozzles of each nozzle row are assigned a young number (# 1, # 2, # 3... #N) in order from the downstream side in the transport direction. Since the first head 410 and the second head 420 are both provided on the carriage 31, when the carriage 31 moves in the movement direction, the first head 410 and the second head 420 also move in the same direction (movement direction). Then, ink is intermittently ejected while the first head 410 and the second head 420 are moving, so that a dot row along the moving direction is formed on the paper S.

<Printing procedure>
When receiving a print command and print data from the computer 110, the controller 60 analyzes the contents of various commands included in the print data and performs the following processing using each unit.

  First, the controller 60 rotates the paper feed roller 21 and sends the paper S to be printed to the conveyance roller 23. Next, the controller 60 rotates the transport roller 23 by driving the transport motor 22. When the transport roller 23 rotates with a predetermined rotation amount, the paper S is transported with a predetermined transport amount.

  When the paper S is conveyed to the lower part of the head unit 40, the controller 60 rotates the carriage motor 32 based on the print command. In response to the rotation of the carriage motor 32, the carriage 31 moves in the movement direction. Further, as the carriage 31 moves, the head unit 40 provided on the carriage 31 also moves in the moving direction at the same time. Then, the controller 60 intermittently ejects ink droplets from the first head 410 and the second head 420 while the head unit 40 is moving in the movement direction. When the ink droplets land on the paper S, a dot row in which a plurality of dots are arranged in the moving direction is formed.

  Further, the controller 60 drives the carry motor 22 between the reciprocation of the head unit 40. The transport motor 22 generates a driving force in the rotation direction according to the commanded driving amount from the controller 60. And the conveyance motor 22 rotates the conveyance roller 23 using this drive force. When the transport roller 23 rotates with a predetermined rotation amount, the paper S is transported with a predetermined transport amount. That is, the transport amount of the paper S is determined according to the rotation amount of the transport roller 23. In this manner, the reciprocating movement of the head unit 40 and the conveyance of the paper S are alternately repeated to form dots on each pixel of the paper S. Thus, an image is printed on the paper S.

  Finally, the controller 60 discharges the paper S on which printing has been completed by the paper discharge roller 25 that rotates in synchronization with the transport roller 23.

=== First Embodiment ===
<About test patterns>
In the first embodiment, adjustment (rotation adjustment) performed independently for each head of the head unit 40 will be described. In the following description, the first head 410 is adjusted.

  FIG. 4 is a diagram illustrating an example of a test pattern. In the test pattern of the first embodiment, ink is intermittently ejected from the nozzles of the black ink nozzle row and the magenta ink nozzle row of the first head 410 while the first head 410 is moving in the moving direction. Is formed by. The black circles in the figure indicate dots formed by the nozzles of the black ink nozzle row of the first head 410, and the white circles indicate dots formed by the nozzles of the magenta ink nozzle row of the first head 410.

  The test pattern of this embodiment is formed by using odd-numbered nozzles in the black ink nozzle row and even-numbered nozzles in the magenta ink nozzle row. For example, the uppermost dot row (downstream in the transport direction) in the figure is formed by the # 1 nozzle of the black ink nozzle row. The lower dot row is formed by the # 2 nozzle of the magenta ink nozzle row. Further, the dot row below it is formed by the # 3 nozzle of the black ink nozzle row. Therefore, the interval between the black ink dot rows and the interval between the magenta ink dot rows arranged in the transport method are each twice the nozzle pitch D (2D). In the present embodiment, the nozzle pitch D is 180 dpi. In this case, the interval between the dot rows of each ink is 90 dpi.

  In the first embodiment, the magenta ink nozzle row and the black ink nozzle row are used for printing the test pattern. When the first head 410 is inclined, the interval between the nozzle rows to be used increases. This is because a difference is likely to appear in the positions of the formed dot rows. If two adjacent nozzle rows (for example, a cyan ink nozzle row and a black ink nozzle row) are used, even if the first head 410 is inclined, it is difficult to make a difference in the positions of the formed dot rows. In other words, it is difficult to accurately adjust the first head 410. In this manner, the first head 410 can be adjusted more accurately by using the nozzle row at a position away from the head.

  In this way, the test pattern is arranged with a dot row group composed of black ink dot rows (hereinafter referred to as a black dot row group) arranged at 2D intervals in the carrying direction and at a 2D interval in the carrying direction. A dot row group composed of magenta ink dot rows (hereinafter referred to as a magenta dot row group) is printed. In addition, the black dot row group and the magenta dot row group partially overlap each other in the movement direction. Hereinafter, this overlapping portion (inside the dotted line in the figure) is referred to as an overlapping portion.

  5A to 5C are explanatory diagrams for adjustment of the first embodiment. FIG. 5A shows an ideal state, and FIGS. 5B and 5C show a case where the first head 410 is tilted. As described above, the black dot row group is formed by the odd-numbered nozzles (# 1, # 3, # 5...) Of the black ink nozzle row, and the magenta dot row group is the even-numbered nozzle ( # 2, # 4, # 6...

When the first head 410 is in an ideal state as shown in FIG. 5A, the dot row interval D1 and the interval D2 in the overlapping portion in the drawing are the nozzle pitch D.
However, when the first head 410 is inclined as shown in FIG. 5B, the distance D1> the distance D2. That is, the interval D1 is larger than the nozzle pitch D, and the interval D2 is smaller than the nozzle pitch D. In this case, the first head 410 may be rotated in the direction of the arrow in FIG. 5B.
When the first head 410 is inclined as shown in FIG. 5C, the distance D1 <the distance D2. That is, the interval D1 is smaller than the nozzle pitch D, and the interval D2 is larger than the nozzle pitch D. In this case, the first head 410 may be rotated in the direction of the arrow in FIG. 5C.

  As described above, the positional relationship between the nozzle rows of the first head 410 is determined by rotating the first head 410 based on the comparison of the dot row intervals (interval D1 and interval D2) of the overlapping portions of the test pattern. Can be adjusted.

  If this dot row interval comparison is performed by visual judgment by an operator, the accuracy is limited, and the comparison result may vary depending on the operator. Further, in the case of visual observation, judgment is often made by looking at a part of a large number of overlapping dot rows. For example, if there is a variation in the ejection direction or the like in the nozzles that form the dot rows in that portion, the dot row intervals cannot be accurately compared. Therefore, in this embodiment, the accuracy of adjustment is increased by using FFT analysis (frequency analysis).

<Regarding Adjustment Process of First Embodiment>
Next, the adjustment process of the first embodiment will be described.
FIG. 6 is a flowchart of the adjustment process according to the first embodiment.

  First, the computer 110 prints a test pattern as shown in FIG. 4 on the paper S by using predetermined nozzles of the black ink nozzle row and the magenta ink nozzle row of the first head 410 of the printer 1 (S101).

  After printing the test pattern, the computer 110 reads an image of the test pattern with the scanner 120 (reading unit) at a reading resolution of, for example, 1440 dpi (S102). In this embodiment, since the dot row interval of each dot row group of the test pattern is 90 dpi, the dot row interval corresponds to 16 pixels of the read image. When the test pattern is read by the scanner 120, the test pattern may be inclined and placed on the document table. In such a case, the computer 110 corrects the inclination of the image read by the scanner 120. By this inclination correction, the period (frequency) at which the peak of the power spectrum appears in the read image can be matched with the theoretical value.

  In this embodiment, the scanner 120 is used to read an image. However, any apparatus that can measure the density distribution along the conveyance direction of the overlapping portion of the test pattern may be used. For example, a microdensitometer that performs one-dimensional concentration measurement may be used.

  The computer 110 cuts out the overlapping portion of the read image (S103), and converts the two-dimensional image of the overlapping portion into a one-dimensional image (S104).

7A to 7C are schematic diagrams for explaining this processing.
FIG. 7A is a diagram showing a read image of the test pattern, FIG. 7B is a diagram showing an image after the overlapping portion of the test pattern is cut out, and FIG. 7C is a diagram showing a one-dimensional image of the overlapping portion. In FIG. 7C, the vertical axis indicates the position in the transport direction, and the horizontal axis indicates the density.

  First, the image of FIG. 7A is obtained by reading the image of the test pattern with the scanner 120. By cutting out the overlapping portion in FIG. 7A, a two-dimensional image (FIG. 7B) of the overlapping portion is obtained. The computer 110 calculates a density (average value) for each column of pixels arranged in the moving direction (hereinafter referred to as a pixel column) in the two-dimensional image of the overlapping portion.

  Then, the computer 110 creates a one-dimensional image as shown in FIG. 7C by associating the position (in the transport direction) of the pixel row with the calculated density. As can be seen from the figure, the density is high at the position corresponding to the dot row in FIG. 7B. In other words, from the density peak in FIG. 7C, the position in the transport direction of the pixel in which the dot row is formed is known.

  It should be noted that the computer 110 also performs the same operation for each pixel column in the transport direction in the portion S1 and the portion S2 in FIG. 7A in which the dot rows of the respective dot row groups are formed independently without overlapping. The density is calculated and a one-dimensional image as shown in FIG. 7C is created. A direction (adjustment direction) in which the first head 410 is rotated is determined using this one-dimensional image (described later).

  Subsequently, the computer 110 performs FFT analysis of the overlapping portion based on the FFT analysis program stored in the memory 113 (S105).

  8A to 8I are explanatory diagrams of the FFT analysis according to the shift amount. In each of FIGS. 8A to 8I, the diagram on the left side is a diagram showing the position (shift) of the black ink dot row (black) and the magenta ink dot row (gray) in the overlapping portion, and the middle figure is It is a figure which shows a one-dimensional image, The figure on the right side is a figure which shows the result of having carried out FFT analysis of the one-dimensional image. In the one-dimensional image, the horizontal axis indicates the reading position (pixel position in the transport direction), and the vertical axis indicates the reading value (density value). In the FFT analysis results, the horizontal axis indicates the period, and the vertical axis indicates the magnitude (intensity) of the power spectrum.

  In the following description, the case where the positions in the transport direction of the two types of dot rows in the overlapping portion of the test pattern are the same is defined as “zero deviation”. Further, when the positions in the transport direction of the two types of dot rows differ by one pixel, the “deviation amount 1” is set. A case where the positions in the transport direction of the two types of dot rows differ by n pixels is defined as “deviation amount n”. That is, in a state where the black ink dot row and the magenta ink dot row are arranged at equal intervals (ideal state), the shift amount is 8 (half of 16 pixels). In the present embodiment, when each dot row is formed in an overlapping manner, the density of that portion (pixel row) is increased (doubled).

  When the amount of deviation is zero (FIG. 8A), the black ink dot row and the magenta ink dot row are printed in an overlapping manner. For this reason, the peak value of the density of the one-dimensional image when the shift amount is zero is twice the peak value of the one-dimensional image in the other figures (FIGS. 8B to 8I). When the amount of deviation is zero, the peak of the power spectrum is large in the vicinity of each dot row interval period (16 periods) of the FFT analysis result, and the peak of the power spectrum of 8 periods, which is half of 16 periods, is also large.

When the shift amount is 1 to 4 (FIGS. 8B to 8E), every time the shift amount increases, the peak of the power spectrum that appears in 16 cycles decreases, and the peak of the power spectrum that appears in 8 cycles also decreases. Note that the amount of change in the power spectrum with respect to the shift amount is larger in 8 cycles than in 16 cycles. For this reason, when the amount of deviation is 4, the peak of the power spectrum that appears in 16 cycles is about half that of the case where the amount of deviation is zero, whereas the power spectrum that appears in 8 cycles is almost zero (minimum value). ing.
When the amount of deviation is 5 to 7 (FIGS. 8F to 8H), every time the amount of deviation increases, the peak of the power spectrum that appears in 16 cycles decreases, and the peak of the power spectrum that appears in 8 cycles increases.
Then, in the ideal state deviation amount 8 (FIG. 8I), the peak of the power spectrum appearing in 8 cycles becomes the maximum, and the power spectrum appearing in 16 cycles becomes almost zero (minimum value).

From the above, in order to arrange the dot rows of each dot row group alternately at equal intervals, the power spectrum that appears in the period of the ideal dot row interval (8 cycles in the present embodiment) is higher than that before the adjustment. The power spectrum that appears after the adjustment is made larger and the power spectrum that appears in the period of the dot row interval of each dot row group (16 cycles in this embodiment) is smaller after the adjustment than before the adjustment. You can see that
Data indicating the FFT analysis result is stored in the memory 113 of the computer 110 in advance.

  The computer 110 performs an FFT analysis of the overlapping part of the test pattern, and compares the analysis result with the data stored in the memory 113. Specifically, in the FFT analysis result, the magnitude of the power spectrum peak appearing in 8 cycles and the magnitude of the power spectrum peak appearing in 16 cycles are compared with the data shown in FIGS. 8A to 8I. Based on the comparison, a deviation amount is calculated. For example, in the FFT analysis result of the test pattern, when the peak value of the power spectrum that appears in 8 cycles is 2 and the peak value of the power spectrum that appears in 16 cycles is 3.5, from each data of FIGS. 8A to 8I The deviation amount is determined to be 2.

  For example, the FFT analysis result is almost the same for the deviation amount 2 and the deviation amount −2. In this case, it is not possible to determine to which direction the first head 410 should be rotated based only on the FFT analysis result. Therefore, the computer 110 creates one-dimensional images of the portions (dots S1 and S2 in FIG. 7A) where the dot rows of each dot row group are formed without overlapping, and the black ink is created from the one-dimensional images. The positional relationship between the dot rows of magenta and the dot rows of magenta ink is obtained. For example, similarly to the overlapping portion, the position in the transport direction of the pixel row on which the black ink dot row is formed can be found from the one-dimensional image of the portion S1 in FIG. 7A. Further, the position in the transport direction of the pixel row on which the magenta ink dot row is formed is known from the one-dimensional image of the portion S2 in FIG. 7A. And the space | interval D1 and space | interval D2 between each dot row shown to FIG. 5A-FIG. 5C can be calculated | required from the position of the pixel of the conveyance direction of each dot row. When the distance D1> the distance D2, the first head 410 may be rotated in the direction of the arrow in FIG. 5B. If the distance D1 <the distance D2, the first head 410 may be rotated in the direction of the arrow in FIG. 5C. In this way, the first head 410 is obtained by determining the position in the transport direction of the pixel array in which the black ink dot array is formed and the position in the transport direction of the pixel array in which the magenta ink dot array is formed. The direction of rotating can be determined.

  Then, the computer 110 calculates an adjustment value for obtaining the ideal state based on the difference between the deviation amount 8 in the ideal state and the calculated deviation amount (S106). Here, the adjustment value is a shift amount of the positional relationship between the dot rows of each dot row group necessary for achieving the ideal state. For example, when the deviation amount is 2 as described above, the adjustment value is 6 (= 8-2). In this case, an ideal state can be obtained by adjusting the positional relationship of the dot rows of each dot row group by 6 pixels.

  After calculating the adjustment value, the computer 110 determines whether or not the obtained adjustment value is larger than the threshold value (S107). If it is determined that the adjustment value is larger than the threshold value (YES in S107), the computer 110 performs adjustment to rotate the first head 410 of the printer 1 based on the obtained adjustment value (S108). Thereby, the positional relationship between the black ink nozzle row and the magenta ink nozzle row of the first head 410 is adjusted.

After adjusting the first head 410, the computer 110 returns to step S101 to execute the head position adjustment process again.
On the other hand, if it is determined in S107 that the adjustment value is equal to or smaller than the threshold value (NO in S107), the head adjustment process is terminated.

  Thus, in this embodiment, the image of the black dot row group and the magenta dot row group formed as the test pattern is read by the scanner 120, and the first head 410 is adjusted based on the frequency analysis. Thereby, the adjustment of the head can be automated, and the adjustment accuracy can be increased. Further, when a large number of dot row groups (black dot row groups) and a large number of dot row groups (magenta dot row groups) are respectively formed as in the present embodiment, the averaging effect is obtained by using frequency number analysis. Can be obtained. For example, as described above, when the deviation is determined by visual observation, the determination is often made by looking at the intervals of some nozzle rows. In this case, if there is an influence such as nozzle injection variation in the visually observed part, it is not possible to accurately determine the deviation amount. On the other hand, in the present embodiment, the averaging effect is not easily affected by such an injection variation of the nozzles, so that highly accurate adjustment can be performed.

  Further, in the present embodiment, the power spectrum of 8 periods is larger after the adjustment than before the adjustment, and the power spectrum of 16 periods is smaller after the adjustment than before the adjustment. An adjustment value is obtained. As a result, an accurate adjustment value can be obtained, and the adjustment accuracy can be further improved.

=== Second Embodiment ===
<About test patterns>
In the second embodiment, position adjustment (alignment adjustment) of two heads (first head 410 and second head 420) of the head unit 40 is performed. The test pattern of the second embodiment is the same pattern as that of the first embodiment (FIG. 4). However, the nozzles for forming each dot row are different from those in the first embodiment. Hereinafter, the test pattern of the second embodiment will be described with reference to FIG.

  In the test pattern of the second embodiment, while the head unit 40 is moving in the moving direction, ink is intermittently discharged from the nozzles of the same color nozzle row (referred to as the black ink nozzle row) of the first head 410 and the second head 420. It is formed by being injected. The black circles in the figure indicate dots formed by the nozzles of the black ink nozzle row of the second head 420, and the white circles indicate dots formed by the nozzles of the black ink nozzle row of the first head 410.

  In the second embodiment, even number nozzles in the black ink nozzle row of the first head 410 are used, and odd number nozzles in the black ink nozzle row of the second head 420 are used to form a test pattern. ing. For example, the uppermost dot row (downstream in the transport direction) in the figure is formed by the # 1 nozzle of the black ink nozzle row of the second head 420. The lower dot row is formed by the # 2 nozzle of the black ink nozzle row of the first head 410. Further, the lower dot row is formed by the # 3 nozzle of the black ink nozzle row of the second head 420. Also in this case, the interval between the dot rows arranged in the transport method formed for each head is twice the nozzle pitch D (2D). In this embodiment, since the nozzle pitch D is 180 dpi, the interval between the dot rows formed for each head is 90 dpi.

  Thus, the test pattern includes a dot row group (hereinafter referred to as a preceding dot row group) composed of dot rows arranged at 2D intervals in the transport direction formed by the nozzle rows of the first head 410, and the second head. A dot row group (hereinafter referred to as a subsequent dot row group) composed of dot rows arranged at intervals of 2D in the transport direction formed by the 420 nozzle rows is printed. In addition, in the preceding dot row group and the subsequent dot row group, some of the positions in the movement direction overlap (overlapping portion).

  FIG. 9A to FIG. 9C are explanatory diagrams for adjustment in the second embodiment. FIG. 9A shows an ideal state, and FIGS. 9B and 9C show a case where the positions of the first head 410 and the second head 420 in the transport direction are shifted. As described above, the preceding dot row group is formed by the even-numbered nozzles (# 2, # 4, # 6...) Of the black ink nozzle row of the first head 410, and the subsequent dot row group is the second head 420. Are formed by odd-numbered nozzles (# 1, # 3, # 5...) Of the black ink nozzle row.

As shown in FIG. 9A, when the positions of the first head 410 and the second head are in an ideal state, the dot row interval D1 and the interval D2 in the overlapping portion in the figure are the nozzle pitch D.
However, when the positions of the first head 410 and the second head 420 are shifted (in the transport direction) as shown in FIG. 9B, the distance D1> the distance D2. That is, the interval D1 is larger than the nozzle pitch D, and the interval D2 is smaller than the nozzle pitch D. In this case, the first head 410 may be moved in the direction of the dotted arrow in FIG. 9B.
If the positions of the first head 410 and the second head 420 are shifted (in the transport direction) as shown in FIG. 9C, the interval D1 <the interval D2. That is, the interval D1 is smaller than the nozzle pitch D, and the interval D2 is larger than the nozzle pitch D. In this case, the first head 410 may be moved in the direction of the arrow indicated by the dotted line in FIG. 8C. 9B and 9C, the second head 420 may be moved in the direction opposite to the dotted arrow.

  In this way, by moving the first head 410 or the second head 420 based on the comparison of the dot row intervals (interval D1 and interval D2) of the overlapping portions of the test pattern, each nozzle row of the first head 410 is moved. And the positional relationship of the nozzle rows of the second head 420 in the transport direction can be adjusted.

<Regarding Adjustment Process of Second Embodiment>
Also in the second embodiment, similarly to the first embodiment, the test pattern is read by the scanner 120, the overlapped portion of the read image is converted into a one-dimensional image, and FFT analysis is performed to obtain the shift amount of the overlapped portion. be able to. And the adjustment value for making it an ideal state can be calculated | required from deviation | shift amount. In the first embodiment, the first head 410 is rotated based on the adjustment value, whereas in the second embodiment, the positional relationship in the transport direction between the first head 410 and the second head 420 based on the adjustment value. The point to adjust is different. For example, when the shift amount calculated by FFT analysis is 2, since the shift amount in the ideal state is 8, the position of the head (for example, the first head 410) for 6 (= 8-2) pixels of the difference is adjusted. What should I do?

  Also in the second embodiment, in order to determine the adjustment direction, a one-dimensional image of a portion where the dot rows of each dot row group are formed without overlapping (the portions S1 and S2 in FIG. 7A) is created. From the one-dimensional image, the positional relationship between the heads is obtained to determine the adjustment direction. For example, the position in the transport direction of the pixel row in which the dot row is formed by the nozzles of the second head 420 is known from the one-dimensional image of the portion S1 in FIG. 7A. Further, the position in the transport direction of the pixel row in which the dot row is formed by the nozzles of the first head 410 is known from the one-dimensional image of the portion S2 in FIG. 7A. Then, the interval D1 and the interval D2 between the dot rows shown in FIGS. 9A to 9C can be obtained from the positions of the pixels in the transport direction of the pixel rows. When the distance D1> the distance D2, the first head 410 may be moved in the direction of the dotted arrow in FIG. 9B. If the distance D1 <the distance D2, the first head 410 may be moved in the direction of the dotted arrow in FIG. 9C. 9B and 9C, the second head 420 may be moved in the direction opposite to the dotted arrow.

  According to the second embodiment, the positional relationship between each nozzle row of the first head 410 and each nozzle row of the second head 420 can be adjusted with high accuracy.

  Note that the adjustment processing of the present embodiment can be similarly applied to the position adjustment of each head of a printer having three or more heads.

=== Third Embodiment ===
In the third embodiment, a case will be described in which the adjustment of ejection timing (Bi-d adjustment) is performed in the forward path and the backward path when bidirectional printing is performed in the reciprocating movement of the head unit 40. In the present embodiment, adjustment is performed using the first head 410.

<About Bi-d adjustment>
When bidirectional printing is performed, the movement direction of the carriage 31 (that is, the movement direction of the head unit 40) is different between the forward path and the return path. Ink must be ejected in position.
Therefore, in the forward path and the return path, ink is ejected from the head nozzle array (for example, the black ink nozzle array) to create a test pattern, and based on the result, the ink ejection timing is adjusted by Bi-d adjustment. It is.

  10A and 10B are explanatory diagrams of test patterns for Bi-d adjustment created in the third embodiment. FIG. 10A is a diagram illustrating a pattern formed in the forward path, and FIG. 10B is a diagram illustrating a pattern formed in the forward path and the return path. The white circles in the figure indicate dots formed in the forward path, and the black circles indicate dots formed in the backward path.

  First, in the forward path, ink is ejected from each nozzle of a nozzle row (for example, a black ink nozzle row) of the first head 410 at a constant cycle. As a result, as shown by white circles in FIG. 10A, a dot row group (hereinafter, referred to as a forward dot row group) composed of dot rows arranged at equal intervals in the movement direction is formed. In this embodiment, for the sake of convenience, the interval between each dot row in the forward dot row group is set to twice the nozzle pitch D (2D).

  Next, in the return path, ink is ejected from the nozzles in the same nozzle array (black ink nozzle array) as in the forward path at the same cycle as in the forward path. As a result, as shown by the black circles in FIG. 10B, a dot row group (hereinafter referred to as a return dot row group) composed of dot rows arranged at equal intervals in the movement direction is formed. The interval between the dot rows in the backward dot row group is also twice the nozzle pitch D (2D). In the forward path, a dot row is formed by a plurality of nozzles on the downstream side in the transport direction, and in the return path, a dot row is formed by a plurality of nozzles on the upstream side in the transport direction from the forward path. Further, the two dot row groups (the forward pass dot row group and the backward pass dot row group) are formed so that the positions in the transport direction overlap at least partially (overlapping portions).

  In the present embodiment, the ejection timing is adjusted so that the dot rows of the forward pass dot row group and the dot rows of the backward pass dot row group are arranged at equal intervals in the overlapping portion. That is, in the overlapping portion, the dot state of the forward pass dot row group and the dot row of the backward pass dot row group are alternately arranged at equal intervals (when the dot row interval of the overlapping portion is the nozzle pitch D) is an ideal state. Accordingly, this Bi-d adjustment test pattern has the same shape as the test pattern of the above-described embodiment.

  Also in this case, similarly to the above-described embodiment, the test pattern is read by the scanner 120, the overlapped portion of the read image is converted into a one-dimensional image, and FFT analysis is performed to obtain the shift amount of the overlapped portion. . Since the shape of the test pattern is the same as that of the above-described embodiment, the ideal dot row interval (shift amount) in the read image read under the same conditions as in the above-described embodiment is 8 pixels.

  Then, the adjustment value is calculated based on the difference between the deviation amount obtained from the test pattern and the deviation amount in the ideal state. In the third embodiment, the ink ejection timing is adjusted based on this adjustment value. For example, when the return dot row group is deviated toward the return direction in the movement direction, the injection timing on the return path is advanced. On the other hand, when the backward dot group is shifted to the forward direction in the movement direction, the injection timing in the backward direction is delayed.

  In the present embodiment, the test pattern is set as an ideal state when the dot rows of the forward dot row group and the dot rows of the backward dot row group are alternately arranged at equal intervals (when the dot row interval of the overlapping portion is 8 pixels). Although formed, it is not limited to this. For example, the test pattern may be formed so that the dot rows in the forward dot row group overlap the dot rows in the backward dot row group. In this case, the ideal state is obtained when the shift amount is zero (when the dot row interval of the overlapping portion is 16 pixels). At this time, as shown in FIGS. 8A to 8I, the power spectrum of 8 cycles and the power spectrum of 16 cycles are both larger than those of other shift amounts. Therefore, the adjustment value may be obtained from the difference between the deviation amount obtained from the FFT analysis result of the test pattern and the deviation amount in the ideal state (zero deviation amount).

  As described above, also in Bi-d adjustment, the accuracy of adjustment of ink ejection timing can be improved by using FFT analysis.

=== Fourth Embodiment ===
The adjustment method of the first embodiment or the second embodiment described above may be applied to a line printer (referred to as printer 1 ') having a nozzle row in which a plurality of nozzles are arranged in the paper width direction.

  FIG. 11 is a block diagram of the overall configuration of the printer 1 ′. FIG. 12A is a cross-sectional view of the printer 1 ′. FIG. 12B is a diagram illustrating a state in which the printer 1 ′ transports the paper S. 11, FIG. 12A and FIG. 12B, the same parts as those in FIG. 1 and FIG. The printer 1 'has a transport unit 20' and a head unit 40 '.

  The transport unit 20 ′ is for transporting the paper S in the transport direction. The transport unit 20 ′ includes a paper feed roller 21, an upstream roller 23 </ b> A, a downstream roller 23 </ b> B, and a transport belt 28. The paper feed roller 21 is a roller for automatically feeding the paper S inserted into the paper insertion opening onto the transport belt 28 in the printer 1. The conveyor belt 28 is provided in a ring shape around the upstream roller 23A and the downstream roller 23B. Then, the conveyor belt 28 rotates in response to the rotation of the upstream roller 23A and the downstream roller 23B. Thereby, the paper S on the transport belt 28 is transported in the transport direction.

  The head unit 40 ′ is for ejecting ink onto the paper S and has a plurality of heads. In this embodiment, there are two heads arranged in the transport direction. A head located on the upstream side in the transport direction is referred to as a first head 410A, and a head located downstream from the first head 410A is referred to as a second head 420B. A plurality of nozzles that are ink ejecting portions are provided on the lower surface of each head.

<About the configuration of the head unit>
FIG. 13 is an explanatory diagram of the configuration of the head unit 40 ′. Here, the head unit 40 ′ is seen from the top of the printer 1.

  The first head 410A and the second head 420B are provided side by side in the transport direction. Each head has a plurality of nozzle rows in which a plurality of nozzles are arranged at intervals of the nozzle pitch D in the paper width direction. In the case of FIG. 13, each head has four nozzle rows (from the left, a magenta (M) ink nozzle row, a yellow (Y) ink nozzle row, a cyan (C) ink nozzle row, and a black (K) ink nozzle row). ing. In addition, the nozzles in each nozzle row are assigned a young number (# 1, # 2, # 3... #N) in order from the right side in the paper width direction. The length in the paper width direction of each nozzle row is equal to or longer than the length in the paper width direction of the paper S to be printed.

<Printing procedure>
When receiving a print command and print data from the computer 110, the controller 60 analyzes the contents of various commands included in the print data and performs the following processing using each unit.

  First, the controller 60 rotates the paper feed roller 21 to send the paper S to be printed onto the transport belt 28. Then, the controller 60 rotates the transport belt 28 by rotating the upstream roller 23A and the downstream roller 23B. As a result, the paper S is transported on the transport belt 28 without stopping at a constant speed, and passes under the first head 410A and the second head 420B. While the sheet S passes under each head, ink is intermittently ejected from each nozzle. As a result, a dot row composed of a plurality of dots along the transport direction is formed on the paper S. Finally, the controller 10 discharges the paper S on which image printing has been completed.

<About head adjustment>
Even in the case of this printer 1 ', the head can be adjusted in the same manner as in the first and second embodiments. However, in the case of the printer 1 ′, the dot rows of each dot row group are formed side by side in the paper width direction.

  For example, when the test pattern is formed using the even-numbered nozzles of the magenta ink nozzle row of the first head 410A and the odd-numbered nozzles of the black ink nozzle row, a group of black dot rows arranged at 2D intervals in the paper width direction; A magenta dot row group arranged at 2D intervals in the paper width direction is printed. In this case, the inclination of the first head 410A can be adjusted by the same processing as in the first embodiment.

  For example, when a test pattern is formed using the odd-numbered nozzles of the black ink nozzle row of the first head 410A and the even-numbered nozzles of the second head 420B, a dot row group (preceding) is arranged at 2D intervals in the paper width direction. Dot row group) and dot row groups (following dot row groups) arranged at 2D intervals in the paper width direction are printed. In this case, the positional relationship in the paper width direction between the first head 410A and the second head 420B can be adjusted by the same processing as in the second embodiment.

  As described above, by applying the adjustment method of this embodiment also to the line printer, it is possible to increase the accuracy of the head adjustment.

=== Other Embodiments ===
The above embodiment is mainly described for a printer. Among them, a printing apparatus, a recording apparatus, a liquid ejecting apparatus, a printing method, a recording method, a liquid ejecting method, a printing system, a recording system, and a computer system are included. Needless to say, the disclosure includes a program, a storage medium storing the program, a display screen, a screen display method, a printed material manufacturing method, and the like.

  Moreover, although the printer etc. as one embodiment were demonstrated, said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About the printer>
In the above-described embodiment, the printer has been described. However, the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, liquid vaporizer, organic EL manufacturing apparatus (particularly polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technique as that of the present embodiment may be applied to various recording apparatuses to which an ink jet technique is applied such as an apparatus and a DNA chip manufacturing apparatus. These methods and manufacturing methods are also within the scope of application.

<About ink>
Since the above-described embodiment was an embodiment of a printer, dye ink or pigment ink was ejected from the nozzle. However, the liquid ejected from the nozzle is not limited to such ink. For example, liquids (including water) including metal materials, organic materials (especially polymer materials), magnetic materials, conductive materials, wiring materials, film forming materials, electronic ink, processing liquids, gene solutions, etc. are ejected from nozzles. May be.

<About test patterns>
The test pattern used for adjustment is not limited to that shown in FIG. 4 as long as the dot rows of each dot row group are at least partially overlapped. For example, the test pattern may be formed so that the dot row interval of each dot row group is four times (4D) the nozzle pitch D. In this case, the dot row interval of the overlapping portion in the ideal state is 2D.

<About head placement>
In the second embodiment, the heads having the same shape (the first head 410 and the second head 420) are arranged side by side at the same position in the transport direction. For example, each head is half the nozzle pitch D in the transport direction (D / 2) You may arrange so that it may shift. In this case, for example, by using each nozzle of the black ink nozzle row of the first head 410 and each nozzle of the black ink nozzle row of the second head 420, a test pattern similar to FIG. 4 can be formed. However, at this time, the dot row interval of each dot row group formed in the test pattern is D, and the dot row interval of the overlapping portion in the ideal state is D / 2. Also in this case, the positional relationship in the transport direction of each head can be adjusted by performing FFT analysis of the test pattern. Similarly, in the fourth embodiment, two heads (the first head 410A and the second head 420B) may be arranged so as to be shifted by a half (D / 2) of the nozzle pitch D in the paper width direction.

1 is a block diagram illustrating a configuration of a printing system. FIG. 2A is a schematic view of the printer 1, and FIG. 2B is a cross-sectional view of the printer 1. 4 is an explanatory diagram of a configuration of a head unit 40. FIG. It is a figure which shows an example of a test pattern. 5A to 5C are explanatory diagrams for adjustment of the first embodiment. FIG. 5A is a diagram illustrating an ideal state, and FIGS. 5B and 5C are diagrams illustrating a case where the first head 410 is tilted. It is a flowchart of the adjustment process of 1st Embodiment. 7A to 7C are schematic diagrams for explaining processing for converting a two-dimensional image into a one-dimensional image. FIG. 7A is a diagram showing a read image of the test pattern, FIG. 7B is a diagram showing an image after the overlapping portion of the test pattern is cut out, and FIG. 7C is a diagram showing a one-dimensional image of the overlapping portion. It is explanatory drawing of FFT analysis in case deviation | shift amount is zero. It is explanatory drawing of the FFT analysis in case deviation | shift amount is 1. FIG. It is explanatory drawing of the FFT analysis in case deviation | shift amount is 2. FIG. It is explanatory drawing of the FFT analysis in case deviation | shift amount is 3. FIG. It is explanatory drawing of the FFT analysis in case deviation | shift amount is 4. It is explanatory drawing of FFT analysis in case deviation | shift amount is 5. FIG. It is explanatory drawing of FFT analysis in case deviation | shift amount is 6. FIG. It is explanatory drawing of the FFT analysis in case deviation | shift amount is 7. It is explanatory drawing of the FFT analysis in case deviation | shift amount is 8. 9A to 9C are explanatory diagrams for adjustment in the second embodiment. FIG. 9A is a diagram illustrating an ideal state, and FIGS. 9B and 9C are diagrams illustrating a case where the positions of the first head 410 and the second head 420 are shifted in the transport direction. 10A and 10B are explanatory diagrams of test patterns for Bi-d adjustment created in the third embodiment. It is a whole block diagram of printer 1 'of 4th Embodiment. FIG. 12A is a cross-sectional view of the printer 1 ′. FIG. 12B is a diagram illustrating a state in which the printer 1 ′ transports the paper S. It is explanatory drawing of a structure of head unit 40 '.

Explanation of symbols

1 printer,
20, 20 'transport unit, 21 paper feed roller, 22 transport motor,
23 transport roller, 23A upstream roller, 23B downstream roller,
24 platen, 25 paper discharge roller, 26, 27 driven roller, 28 transport belt,
30 Carriage unit, 31 Carriage, 32 Carriage motor,
40, 40 'head unit, 50 detector group, 51 linear encoder,
52 rotary encoder, 53 paper detection sensor, 54 optical sensor,
60 controller, 61 interface unit, 62 CPU, 63 memory,
64 unit control circuit, 110 computer,
111, 122 interface unit, 112, 123 CPU,
113, 124 memory, 120 scanner,
121 reading carriage, 125 scanner controller,
410, 410A first head, 420, 420B second head

Claims (7)

Using a first nozzle row composed of a plurality of nozzles arranged in a predetermined direction to form a first dot row group composed of a plurality of dot rows arranged in the predetermined direction at predetermined intervals;
From a plurality of dot rows arranged in the predetermined direction at the predetermined interval, using a second nozzle row composed of a plurality of nozzles arranged in the predetermined direction at a position at least partially overlapping with the first dot row group. Forming a configured second dot row group;
Reading a pattern formed by the first dot row group and the second dot row group with a reading unit;
Performing frequency analysis of the scanned image;
In the frequency domain, the power spectrum of the frequency corresponding to the ideal dot row interval in the overlapping portion of the first dot row group and the second dot row group is larger after adjustment than before adjustment. Adjusting at least one position of the first nozzle row and the second nozzle row;
An adjustment method comprising: The adjustment method according to claim 1,
When adjusting the positional relationship between the first nozzle row and the second nozzle row, an ideal dot row interval in an overlapping portion of the first dot row group and the second dot row group in the frequency domain So that the power spectrum after the adjustment becomes larger than before the adjustment, and the power spectrum of the frequency corresponding to the predetermined interval becomes smaller after the adjustment than before the adjustment. An adjustment method for adjusting at least one position of the first nozzle row and the second nozzle row. The adjustment method according to claim 1 or 2,
The first nozzle row and the second nozzle row are provided in the same head,
An adjustment method for adjusting the tilt of the head. The adjustment method according to claim 3,
In the head, a plurality of nozzle rows are arranged in a direction intersecting the predetermined direction,
The first nozzle row is a nozzle row on one end side in a direction intersecting the predetermined direction,
The second nozzle row is a nozzle row on the other end side in a direction intersecting the predetermined direction.
Adjustment method. The adjustment method according to claim 1 or 2,
The first nozzle row and the second nozzle row are provided in separate heads,
An adjustment method for adjusting the positional relationship of each head in the predetermined direction. An adjustment method according to any one of claims 1 to 5,
An adjustment method for obtaining a positional relationship between a dot row of the first dot row group and a dot row of the second dot row group in a non-overlapping portion and determining an adjustment direction based on the result. Forming a first dot row group constituted by a plurality of dot rows arranged in a direction intersecting the predetermined direction at predetermined intervals using a nozzle row constituted by a plurality of nozzles arranged in a predetermined direction;
A second dot row group composed of a plurality of dot rows arranged in a direction intersecting the predetermined direction at the predetermined interval using the nozzle row at a position at least partially overlapping with the first dot row group. Forming,
Reading a pattern formed by the first dot row group and the second dot row group with a reading unit;
Performing frequency analysis of the scanned image;
In the frequency domain, the power spectrum of the frequency corresponding to the ideal dot row interval in the overlapping portion of the first dot row group and the second dot row group is larger after adjustment than before adjustment. Adjusting the ejection timing from the nozzle row when forming the first dot row group and the second dot row group;
An adjustment method comprising: