Printing system, method for correcting landing position, and control device

Abstract

The present invention corrects the landing position of ink while reducing the drawing area required for printing a correction pattern.　Provided is a printing device comprising a head unit 12, an optical sensor 104, and a control unit 30. The printing device uses a correction pattern including: a reference pattern in which patches associated with the amount of deviation in landing position are arranged, and which indicates a reference state corresponding to the amount of deviation by drawing that uses only a reference nozzle row; and a target pattern which includes a patch that is drawn using a plurality of nozzle rows including a target nozzle row that is subject to landing position correction. The control unit 30 determines the amount of deviation in landing position between the reference nozzle row and the target nozzle row from the amount of reflected light from the positions of a plurality of patches in the reference pattern and from the amount of reflected light from the position of the patch in the target pattern; and corrects the landing position on the basis of the determined amount of deviation.

Description

Printing system, landing position correction method, and control device

[0001] The present invention relates to a printing system, a landing position correction method, and a control device.

[0002] Conventionally, printing apparatuses that perform printing by an inkjet method have been widely used. Further, regarding such printing apparatuses, a configuration is known that adjusts the deviation amount of the ejection timing (recording timing) between a plurality of nozzle rows (for example, refer to Patent Document 1).

[0003] Japanese Patent No. 5664045

[0004] In a printing apparatus, if an error occurs in the ejection timing between a plurality of nozzle rows, a deviation occurs in the landing position of ink ejected from the nozzles. In this case, it is necessary to correct the landing position by adjusting the ejection timing. It is desirable to automate this landing position correction. For example, it is conceivable to perform landing position correction (adjustment) by causing the printing apparatus to print a predetermined correction pattern, and detecting reflected light from the pattern using a light detection mechanism such as a reflective photosensor.

[0005] To correct the ink landing position, for example, it is conceivable to perform the landing position correction by adjusting the ejection timing of a plurality of other nozzle rows with one nozzle row as a reference. In this case, normally, it is necessary to print a plurality of patches of a predetermined pattern for each combination of the reference nozzle row and the correction target nozzle row. Therefore, when the number of nozzle rows provided in the printing apparatus increases, the number of nozzle rows targeted for landing position correction increases, which increases the drawing area for printing the correction pattern on the medium. As a result, problems arise such as an increase in the consumption (usage amount) of medium and ink consumed for landing position correction (a problem of increased cost), and an increase in the time required for printing the correction pattern and detecting the deviation amount. Therefore, conventionally, a correction pattern that requires a smaller drawing area has been desired. Accordingly, an object of the present invention is to provide a printing system, a landing position correction method, and a control device that can solve the above problems.

[0006] The inventors of this application have diligently researched methods to reduce the required printing area for correction patterns used to correct deviations in the impact position. They have found that by using a correction pattern that includes a predetermined reference pattern that indicates a reference state corresponding to the amount of deviation in the impact position by being drawn using only a reference nozzle row, and a predetermined target pattern that includes patches drawn using multiple nozzle rows, including the nozzle row to be corrected for the impact position, the printing area required for printing the correction pattern can be reduced. Furthermore, through further diligent research, the inventors of this application have identified the features necessary to obtain such an effect, leading to the present invention.

[0007] To solve the above problems, the present invention provides a printing system that performs printing by an inkjet method, comprising: a head unit having a nozzle row in which a plurality of nozzles are arranged; a main scanning drive unit that causes the head unit to perform a main scanning operation in which ink is ejected while moving in the main scanning direction relative to the medium to which the ink is to be ejected; a light detection mechanism that detects reflected light from a correction pattern which is a pattern used to correct the deviation of the landing position of the ink ejected from the nozzles of the nozzle row; and a control unit that controls the operation of the head unit and the main scanning drive unit so as to cause the head unit to draw the correction pattern and corrects the landing position based on the reflected light detected by the light detection mechanism, wherein the head unit has a plurality of nozzle rows, and the correction pattern is a unit pattern corresponding to the amount of deviation of the landing position. The system includes a reference pattern which is a pattern of patches arranged in a row and is drawn using only one of the reference nozzle rows which is one of the nozzle rows in the head unit, thereby serving as a reference pattern for determining the amount of deviation, and which includes a plurality of patches corresponding to different amounts of deviation from each other, and a target pattern which is a pattern which includes the patches drawn using a plurality of nozzle rows which is the nozzle row that is the target of the correction of the impact position, and the control unit determines the amount of deviation of the impact position that occurs between the reference nozzle row and the target nozzle row from the amount of reflected light from the positions of the plurality of patches in the reference pattern and the amount of reflected light from the positions of the patches in the target pattern, and corrects the impact position based on the determined amount of deviation.

[0008] This configuration reduces the area required for printing the correction pattern. Furthermore, it reduces the consumption of media and ink used for correcting the impact position, and shortens the time required for printing the correction pattern and detecting the misalignment. In this configuration, the target pattern is a pattern containing patches drawn using a reference nozzle row and a target nozzle row. The amount of reflected light from the patch positions in the target pattern changes according to the amount of misalignment of the impact position between the reference nozzle row and the target nozzle row. In this configuration, if the maximum reflected light amount within a preset range of impact position misalignment is defined as the maximum reflected light amount and the minimum reflected light amount as the minimum reflected light amount, the reference pattern includes a maximum reflected light amount corresponding patch and a minimum reflected light amount corresponding patch. With this configuration, the reference pattern can indicate a reference state corresponding to the amount of misalignment of the impact position. Furthermore, the reference pattern may include a mid-reflectance corresponding patch, which corresponds to a light intensity greater than the minimum reflected light intensity and less than the maximum reflected light intensity. With this configuration, the reference pattern can more precisely indicate the reference state corresponding to the amount of deviation in the impact position.

[0009] Furthermore, in this configuration, the patch of the target pattern can be a pattern formed by overlapping predetermined unit patterns. Suitable unit patterns include patterns where a predetermined number of patterns with a width of 2N pixels (where N is an integer of 1 or more) in the main scanning direction are arranged with a gap of 2N pixels between them. In the patch of the target pattern, the unit pattern drawn using the reference nozzle row and the unit pattern drawn using the target nozzle row overlap with a position shift of N pixels in the main scanning direction. In this case, the patch of the reference pattern can be a pattern in which a first unit pattern drawn using the reference nozzle row and a second unit pattern drawn using the reference nozzle row overlap. The reference pattern also includes a first patch in which the first and second unit patterns overlap with their positions aligned in the main scanning direction, and a second patch in which the first and second unit patterns overlap with a position shift of 2N pixels in the main scanning direction. With this configuration, the reference pattern can appropriately indicate the reference state corresponding to the amount of deviation in the impact position.

[0010] Furthermore, in this configuration, the print head has multiple target nozzle rows. It is preferable that the number of patches corresponding to one target nozzle row in the target pattern be less than the number of patches included in the reference pattern. For example, one patch. This configuration reduces the print area required for printing the correction pattern. Depending on the accuracy required for correcting the impact position, there may be two or more patches corresponding to one target nozzle row in the target pattern. In addition, in this configuration, the patches in the target pattern have a reference nozzle row corresponding portion, which is drawn using the reference nozzle row, and a target nozzle row corresponding portion, which is drawn using the target nozzle row. As a result, the amount of reflected light changes according to the amount of deviation in the impact position between the reference nozzle row and the target nozzle row.

[0011] Furthermore, in this configuration, the printing system may use a flatbed inkjet printer. In this case, the printing system further includes a table on which the entire medium is placed, and a sub-scanning drive unit that moves the head unit in a sub-scanning direction perpendicular to the main scanning direction. In this case, the control unit causes the head unit to print correction patterns at multiple different positions on the medium placed on the table, and detects the amount of deviation for each of the multiple positions on the table. With this configuration, even when there is a difference in the amount of deviation of the impact position depending on the position on the table, the impact position can be corrected more appropriately. In this case, by using a correction pattern that can reduce the production area, the correction pattern can be printed more flexibly at various positions on the medium on the table. In this case, the control unit may also detect abnormal values ​​included in the detection results based on the detection results of the amount of deviation corresponding to the multiple positions on the table.

[0012] Furthermore, it is also conceivable to use a correction pattern with different characteristics from those described above as a correction pattern that can reduce the production area. For example, an inkjet printing system comprising: a head unit having a nozzle row with multiple nozzles arranged in a line; a main scanning drive unit causing the head unit to perform a main scanning operation in which ink is ejected while moving in the main scanning direction relative to the medium to which the ink is to be ejected; a light detection mechanism for detecting reflected light from a correction pattern, which is a pattern used to correct the misalignment of the landing position of the ink ejected from the nozzles of the nozzle row; and a control unit that controls the operation of the head unit and the main scanning drive unit to cause the head unit to draw the correction pattern and correct the landing position based on the reflected light detected by the light detection mechanism, wherein the head unit has a first nozzle row, which is a first nozzle row, and a second nozzle row, which is a second nozzle row, and the correction pattern is a pattern in which patches, which are unit patterns corresponding to the amount of misalignment of the landing position, are arranged in a line, and the patch in which the amount of reflected light is maximum or minimum changes according to the amount of misalignment, and includes 2N+1 patches corresponding to the amount of misalignment of -N pixels (where N is an integer of 1 or more) or more and +N pixels or less, and the control unit, Based on the detected shift amount, which is the shift amount determined based on the reflected light, the impact position is corrected, and the state in which the amount of reflected light is either maximum or minimum is defined as the first pole state, and the state in which it is the other is defined as the second pole state. When the amount of reflected light in any of the patches reaches the first pole state, the shift amount corresponding to the patch that reached the first pole state is used as the detected shift amount. When the amount of reflected light in any of the patches does not reach the first pole state, and the amount of reflected light from the arranged patches increases or decreases monotonically, the shift amount corresponding to -N pixels or +N pixels is used as the detected shift amount, depending on how the amount of reflected light changes. When the amount of reflected light in any of the patches does not reach the first pole state, and the amount of reflected light from the patch corresponding to the shift amount of +(N-1) pixels reaches the second pole state, the shift amount corresponding to -(N+1) pixels is used as the detected shift amount. When the amount of reflected light in any of the patches does not reach the first pole state, andIf the amount of reflected light from the patch corresponding to the displacement amount of the -(N-1) pixel is in the second polarity state, it is also conceivable to use the displacement amount corresponding to the +(N+1) pixel as the detected displacement amount.

[0013] Even with this configuration, the area required for printing the correction pattern can be reduced. This also makes it possible to reduce the amount of media and ink consumed for correcting the impact position, and to shorten the time required for printing the correction pattern and detecting the amount of deviation. Furthermore, as part of the present invention, it is also possible to consider configurations of impact position correction methods and control devices having the same characteristics as described above. In these cases as well, the same effects as described above can be obtained.

[0014] According to the present invention, it is possible to correct the ink landing position while reducing the production area required for printing the correction pattern.

[0015] This figure illustrates a printing apparatus 10 according to one embodiment of the present invention. Figure 1(a) shows an example of the configuration of the main part of the printing apparatus 10. Figure 1(b) shows an example of the configuration of the head row 102. This figure illustrates an example of a correction pattern. Figure 2(a) shows an example of the configuration of a unit pattern 202, which is a pattern used as a component of the correction pattern. Figures 2(b) and (c) show examples of the configuration of a reference nozzle row corresponding pattern 212 and a target nozzle row corresponding pattern 214. Figure 2(d) shows an example of a change that occurs in the correction pattern according to the amount of deviation of the impact position. This figure illustrates an example of a correction pattern that differs from a standard pattern. Figures 3(a) and (b) show examples of the configuration of a reference nozzle row corresponding pattern 212 and a target nozzle row corresponding pattern 214 in the correction pattern of this example. Figure 3(c) shows an example of the operation of detecting the amount of deviation of the impact position using the correction pattern of this example. This figure further explains in detail the correction of the impact position performed in the printing apparatus 10 of this example. Figure 4(a) shows an example of a pattern used to correct the impact position for multiple nozzle rows that emit different colors. Figure 4(b) shows an example of a normal peak patch and bottom patch. Figure 4(c) shows an example of an ideal peak patch and bottom patch. This figure illustrates an example of features related to the correction pattern in this example. Figure 5(a) shows an example of the configuration of the unit pattern 302 used in the correction pattern in this example. Figure 5(b) shows an example of the change in the amount of reflected light that occurs in a patch using the unit pattern 302 according to the amount of deviation in the impact position. Figure 5(c) shows an example of the change that occurs according to the amount of deviation in the impact position between the reference nozzle row and the target nozzle row when the cyan nozzle row of head 1 in the head section 12 is used as the reference nozzle row and the cyan nozzle rows of heads 2 to 4 are used as the target nozzle row. This figure explains the features of the correction pattern in this example. Figure 6(a) shows an example of the part of the correction pattern in this example that corresponds to multiple nozzle rows for one color. Figure 6(b) shows an example of the configuration of the reference pattern 334. Figure 6(c) shows another example of the patch included in the reference pattern 334. This figure shows an example of the configuration of the printing system 1000 when the impact position is corrected using a control device 1100 located outside the printing device 1200.

[0016] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a diagram illustrating a printing apparatus 10 according to one embodiment of the present invention. Figure 1(a) shows an example of the configuration of the main parts of the printing apparatus 10. Except for the points shown below, the printing apparatus 10 and each part of the printing apparatus 10 in this example may have the same or similar characteristics as known printing apparatuses and each part thereof. In addition, the printing apparatus 10 may further include configurations that are the same or similar as known printing apparatuses, in addition to the illustrated configuration. The printing apparatus 10 in this example is an inkjet printer that performs printing on a medium 50 to which ink is to be ejected using an inkjet method, and comprises a head unit 12, a table 14, a Y bar 16, a main scanning drive unit 18, a sub-scanning drive unit 20, and a control unit 30. Paper, film, etc. can be suitably used as the medium 50. The printing apparatus 10 in this example is also an example of a printing system. For example, the control unit 30 of the printing apparatus 10 is a control unit (control device) of the printing system. In a modified example of the configuration of the printing system, the printing system may be composed of a plurality of devices. For example, a printing system may include a printing device that performs printing and a control device that performs at least some of the functions of the control unit 30 described below.

[0017] The head unit 12 of the printing apparatus 10 is the part that ejects ink onto the medium 50, and has a plurality of inkjet heads for ejecting ink. The head unit 12 in this example has a carriage 100, a plurality of head rows 102, and an optical sensor 104. The carriage 100 is a holding member that holds other components of the head unit 12. The head row 102 is a row in which a plurality of inkjet heads are arranged. The optical sensor 104 is an optical detection mechanism that detects reflected light from the medium 50. As the optical sensor 104, for example, an optical transmitter and receiver having an optical transmitter and an optical receiver can be suitably used. In this case, the optical transmitter irradiates light onto the medium 50, which is the detection object (detection target) for which the reflected light is to be detected, and the optical receiver detects the amount (intensity) of the reflected light from the medium 50. More specifically, as the optical sensor 104, for example, a reflective photosensor such as a known diffuse reflection optical sensor can be suitably used. Furthermore, the optical sensor 104 in this example detects reflected light at a position corresponding to a correction pattern printed on the medium 50. The reflected light at a position corresponding to a correction pattern is the reflected light reflected by the correction pattern or the medium 50 at or near the position where the correction pattern is printed. Also, as described above, the optical sensor 104 in this example is a component of the head unit 12. In other words, the printing device 10 can be considered to have both a head unit 12 and an optical sensor 104 by having a head unit 12. Alternatively, depending on how the configuration of the printing device 10 is divided, the optical sensor 104 can be considered a component other than the head unit 12. In this case, the printing device 10 can be considered to have an optical sensor 104 separately from the head unit 12. Furthermore, the correction pattern in this example uses a pattern for correcting the misalignment of the landing position of ink ejected from the nozzles of one of the nozzle rows of the inkjet heads of the head unit 12.

[0018] Table 14 is a table-shaped member that holds the medium 50 in a position opposite to the head unit 12. In this example, the entire medium 50 is placed on the top surface of Table 14. In other words, the printing device 10 in this example is a flatbed inkjet printer. In a modified configuration of the printing device 10, only a part of the medium 50 may be placed on the top surface of Table 14. In this case, the printing device 10 can be considered as a vertical inkjet printer or the like. Y-bar 16 is a member that holds the head unit 12 in a position opposite to Table 14. In this example, Y-bar 16 has a guide rail that extends in a preset main scanning direction (Y direction in the figure) in the printing device 10, and holds the carriage 100 of the head unit 12 with the guide rail, thereby guiding the movement of the head unit 12 in the main scanning direction and holding the head unit 12 in a position opposite to Table 14.

[0019] The main scanning drive unit 18 is a drive unit that causes the head unit 12 to perform the main scanning operation. The main scanning operation is an operation in which ink is ejected while moving in the main scanning direction relative to the medium 50. In this example, the main scanning drive unit 18 moves the head unit 12 in the main scanning direction by moving the carriage 100 of the head unit 12 along the guide rail of the Y bar 16. The main scanning drive unit 18 causes the head unit 12 to perform the main scanning operation by ejecting ink from the inkjet head, which moves in the main scanning direction together with the carriage 100. The sub-scanning drive unit 20 is a drive unit that causes the head unit 12 to perform the sub-scanning operation. The sub-scanning operation is an operation in which the head unit 12 moves relative to the medium 50 in the sub-scanning direction (X direction in the figure) which is perpendicular to the main scanning direction. In this example, the sub-scanning drive unit 20 moves the head unit 12 together with the Y bar 16 by moving the Y bar 16 in the sub-scanning direction. This causes the sub-scanning drive unit 20 to perform a sub-scanning operation on the head unit 12. By causing the head unit 12 to perform a sub-scanning operation in between main scanning operations, the sub-scanning drive unit 20 changes the position on the medium 50 that is opposite to the head unit 12 when the next main scanning operation is performed.

[0020] The control unit 30, for example, includes the CPU of the printing device 10 and controls the operation of each part of the printing device 10. More specifically, the control unit 30 controls the operation of the head unit 12, the main scanning drive unit 18, and the sub-scanning drive unit 20, etc., based on the print data, causing the head unit 12 to eject ink to the ejection position for drawing the image indicated by the print data. In this example, the control unit 30 also controls the operation of the head unit 12 and the main scanning drive unit 18, etc., causing the head unit 12 to eject ink to the ink ejection position corresponding to the correction pattern. The control unit 30 then corrects the impact position based on the reflected light detected by the optical sensor 104 from the correction pattern. For example, the control unit 30 corrects the impact position by adjusting the ejection timing for ejecting ink to the nozzle row of the inkjet head.

[0021] As described above, the printing apparatus 10 may further include configurations identical or similar to those of known printing apparatuses, in addition to the illustrated configuration. For example, the printing apparatus 10 may further include fixing means for fixing ink to the medium 50. Such fixing means should be tailored to the ink used by the inkjet head of the head unit 12. For example, when using ultraviolet-curable ink, which hardens when exposed to ultraviolet light, a light source that emits ultraviolet light can be used as the fixing means. Alternatively, when using evaporation-drying ink, which is fixed to the medium by drying, a heater or the like that that heats the medium can be used as the fixing means. Furthermore, depending on the characteristics of the ink used, the fixing means may be omitted.

[0022] Furthermore, as described above, the head unit 12 in this example has multiple head rows 102. As shown in Figure 1(b), multiple inkjet heads 120 are arranged in the head row 102. Figure 1(b) shows an example of the configuration of the head row 102. The head row 102 in this example has multiple inkjet heads 120 that are arranged with their positions offset in the sub-scanning direction. These inkjet heads 120 can also be considered to constitute a single virtual inkjet head. In addition, the inkjet head 120 has a nozzle row 122 in which multiple nozzles are arranged with their positions offset in the sub-scanning direction. The inkjet head 120 is an ejection head that ejects ink using an inkjet method. As shown in the figure, the inkjet head 120 in this example has two nozzle rows 122. The two nozzle rows 122 of the inkjet head 120 eject ink of different colors from each other. The head row 102 shown in Figure 1(b) is one of several head rows 102 located in the head unit 12, and has four inkjet heads 120, which are distinguished as head 1 to head 4 in the figure. These inkjet heads 120 have a nozzle row 122 for black (K) ink and a nozzle row 122 for cyan (C) ink. This head row 102 can be thought of as a virtual inkjet head that ejects black and cyan ink.

[0023] Furthermore, the head unit 12 in this example further has a head row 102 that ejects ink of colors other than black and cyan. This head row 102 also has a plurality of inkjet heads 120 (heads 1 to 4), similar to the configuration shown in Figure 1(b), for example. These inkjet heads 120 also have two nozzle rows 122. The inkjet heads 120 of this head row 102 have, for example, a nozzle row 122 for magenta (M color) and a nozzle row 122 for yellow (Y color). The head unit 12 may further have head rows 102 or inkjet heads 120 for other colors other than those mentioned above.

[0024] The printing apparatus 10 in this example ejects ink onto the medium 50 using multiple nozzle rows 122 of the head unit 12. If there is a difference in the landing position of the ink ejected from the nozzles of the nozzle row 122, the print quality will be affected. Therefore, as described above, the printing apparatus 10 in this example detects the deviation in the landing position using a correction pattern and corrects the landing position by adjusting the ejection timing of the ink ejected from the nozzles of the nozzle row based on the detection result. The printing apparatus 10 in this example automatically adjusts the landing position using the correction pattern. The correction pattern will be described in detail below. First, as an example of a correction pattern, an example of a standard pattern will be described. This standard pattern can be used when the increase in the production area required for printing the correction pattern is not a problem. As such a correction pattern, for example, the pattern shown in Figure 2 can be used.

[0025] Figure 2 illustrates an example of a correction pattern, showing an example of the configuration of a correction pattern when a standard pattern is used. Figure 2(a) shows an example of the configuration of a unit pattern 202, which is a pattern used as a component of the correction pattern. A unit pattern 202 is a pattern (identical pattern) that is arranged with a shifted position within the correction pattern. In this example, the unit pattern 202 is a pattern in which multiple rectangular element patterns 200, with the sub-scanning direction as the longitudinal direction, are arranged in the main scanning direction. A rectangular element pattern 200 is a pattern composed of multiple pixels arranged within a rectangular area. These pixels are ink ejected from one nozzle row in one main scanning operation. As an element pattern 200, for example, it is conceivable to use a pattern in which about 3 to 7 pixels are arranged in the main scanning direction and more pixels are arranged in the sub-scanning direction. In this example, the element pattern 200 is a pattern in which 4 pixels are arranged in the main scanning direction and more pixels are arranged in the sub-scanning direction.

[0026] In the unit pattern 202, non-ejection regions, which are areas where ink is not ejected, are provided at positions adjacent to the element patterns 200 in the main scanning direction. In this example, the unit pattern 202 has the same number of non-ejection regions as the element patterns 200, as shown in the figure. The unit pattern 202 can also be considered to have non-ejection regions (gap regions) at one end in the main scanning direction, in addition to the gap regions between the element patterns 200. In this example, the width of the gap region in the main scanning direction is the same as the width of the element pattern 200, which is 4 pixels. The unit pattern 202 in this example includes 4 element patterns 200 and 4 gap regions. In other words, the unit pattern 202 in this example is a pattern in which 4-pixel wide filled areas and 4-pixel wide blank areas are arranged alternately. When drawing the unit pattern 202 on a white medium using black ink, the unit pattern 202 becomes a pattern in which 4-pixel wide black areas and 4-pixel wide white areas are arranged alternately (a pattern of 4 pixels black and 4 pixels white).

[0027] The correction pattern in this example is a pattern (misalignment correction chart) used to correct the misalignment of the landing position of ink ejected from the nozzles of the nozzle row in the printing apparatus 10. It includes a reference nozzle row corresponding pattern 212 drawn with ink ejected from the nozzles of a reference nozzle row, which is any one of the nozzle rows, and a target nozzle row corresponding pattern 214 drawn with ink ejected from the nozzles of a target nozzle row, which is the nozzle row whose landing position is to be corrected. The misalignment of the landing position corrected using the correction pattern is the error in the landing position that occurs when ink is ejected to the same position in the reference nozzle row and the target nozzle row. As the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214, for example, a pattern composed of multiple unit patterns 202 is used, as shown in Figures 2(b) and (c). The reference nozzle row is an example of a first nozzle row, which is the first nozzle row. The target nozzle row is an example of a second nozzle row, which is the second nozzle row. Figures 2(b) and 2(c) show an example of the configuration of the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214. In this example, the reference nozzle row corresponding pattern 212 is a pattern in which a plurality of unit patterns 202 are arranged in the main scanning direction at predetermined intervals. The target nozzle row corresponding pattern 214 is a pattern in which a plurality of unit patterns 202 are arranged in the main scanning direction at intervals different from those of the unit patterns 202 in the reference nozzle row corresponding pattern 212.

[0028] In the configuration shown in Figure 2(b), the reference nozzle row corresponding pattern 212 is a pattern in which seven unit patterns 202 are arranged in the main scanning direction without any gaps. Here, "without any gaps" means that the width of the gap area at the boundary of adjacent unit patterns 202 is the same number of pixels as the other gap areas of that unit pattern 202. In other words, the reference nozzle row corresponding pattern 212 is a pattern in which element patterns 200 are arranged at a constant interval throughout its entirety. Furthermore, the target nozzle row corresponding pattern 214 shown in Figure 2(c) is a pattern in which seven unit patterns 202 are arranged in the main scanning direction with a gap of one pixel between them. Here, "with a gap of one pixel" means that the width of the gap area at the boundary of adjacent unit patterns 202 is one pixel wider than the other gap areas of that unit pattern 202. In other words, the target nozzle row corresponding pattern 214 is a pattern in which the unit patterns 202 are arranged at an interval that is shifted by one pixel compared to the reference nozzle row corresponding pattern 212.

[0029] Furthermore, in the correction pattern of this example, the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 are drawn so that the positions of their unit patterns 202 are aligned at one of the positions and the element patterns 20 overlap. The element patterns 200 overlap at the same position when there is no difference in the impact position between the reference nozzle row and the target nozzle row. The printing apparatus 10 of this example prints the correction pattern so that the central unit pattern 202 in the main scanning direction, among the multiple unit patterns 202 (seven unit patterns 202) that make up the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214, is aligned and overlaps in both the main scanning direction and the sub-scanning direction. The state of the correction pattern actually printed on the medium changes, for example, as shown in Figure 2(d), depending on the amount of difference in the impact position between the reference nozzle row and the target nozzle row.

[0030] Figure 2(d) shows an example of the changes that occur in the correction pattern depending on the amount of deviation in the impact position. For example, as shown in the upper part of Figure 2(d), the part where one unit pattern 202 in the reference nozzle row corresponding pattern 212 and one unit pattern 202 in the target nozzle row corresponding pattern 214 overlap becomes one patch 220. In this example, patch 220 can be thought of as a unit pattern that corresponds to the amount of deviation in the impact position. Patch 220 is a pattern in which the reference nozzle row corresponding part, which is the part drawn using the reference nozzle row, and the target nozzle row corresponding part, which is the part drawn using the target nozzle row, are superimposed, that is, a pattern in which the unit pattern 202 of the reference nozzle row corresponding pattern 212 and the unit pattern 202 of the target nozzle row corresponding pattern 214 are superimposed. In this example, patch 220 is drawn using multiple (two) nozzle rows, including the target nozzle row. As described above, the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 in this example use patterns in which unit patterns 202 are arranged in the main scanning direction at different intervals from each other. Therefore, there is a difference in the way in which the unit patterns 202 of the reference nozzle row corresponding pattern 212 and the unit patterns 202 of the target nozzle row corresponding pattern 214 overlap for each patch 220. For example, when using the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 shown in Figures 2(b) and (c), the relative position of the unit patterns 202 of the target nozzle row corresponding pattern 214 with respect to the unit patterns 202 of the reference nozzle row corresponding pattern 212 in the main scanning direction will shift by one pixel for each patch 220. As a result, when detecting reflected light using the optical sensor 104 (see Figure 1), there is a difference in the amount of reflected light from the position corresponding to each patch 220.

[0031] The upper diagram in Figure 2(d) shows how the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 overlap when there is no shift in the impact position between the reference nozzle row and the target nozzle row. In this example, as indicated by the letter Peak in the figure, the amount of reflected light is at its maximum (peak) at the position of the central patch 220. The central diagram in the vertical direction of Figure 2(d) shows a state where there is a shift in the impact position of -3 pixels relative to a predetermined direction in the main scanning direction between the reference nozzle row and the target nozzle row. In this case, the amount of reflected light is at its maximum at the position of the leftmost patch 220 in the figure. The lower diagram in Figure 2(d) shows a state where there is a shift in the impact position of +3 pixels relative to a predetermined direction in the main scanning direction between the reference nozzle row and the target nozzle row. In this case, the amount of reflected light is at its maximum at the position of the rightmost patch 220 in the figure. Furthermore, although not shown in the diagram, if there is a deviation in the impact position other than those mentioned above within the range of -3 to +3 pixels, the amount of reflected light at the position of patch 220 corresponding to each deviation will be maximized.

[0032] By using a correction pattern that includes a reference nozzle row corresponding pattern 212 and a target nozzle row corresponding pattern 214, the position of the patch 220 where the amount of reflected light is maximized can be detected, thereby identifying the amount of deviation in the impact position between the reference nozzle row and the target nozzle row. This makes it possible to adjust the discharge timing of each nozzle row to eliminate the deviation. In this example, the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214, which are composed of a unit pattern 202 in which 4-pixel wide filled areas and 4-pixel wide blank areas are arranged alternately, are superimposed to create seven patches 220. By detecting the position of the peak patch, which is the patch 220 where the amount of reflected light is maximized among these patches 220, the amount of deviation in the impact position can be identified in the range of -3 pixels to +3 pixels.

[0033] As mentioned above, in the printing device 10, it is sometimes desirable to reduce the production area required for printing the correction pattern. In this case, it is possible to use a correction pattern with the configuration described below using Figure 3. Figure 3 is a diagram illustrating an example of a correction pattern different from the standard pattern described above. Hereafter, for the sake of explanation, the standard pattern described using Figure 2 will be referred to as the standard pattern. The correction pattern described below using Figure 3 will be referred to as the correction pattern of this example. Except for the points described below, the correction pattern of this example may have the same or similar characteristics as the standard pattern. Also, except for the points described below, the components in Figure 3 that are denoted by the same reference numerals as in Figure 2 may be considered to be the same or similar components as those in Figure 2.

[0034] The correction pattern in this example, like the standard pattern, includes a reference nozzle row corresponding pattern 212 and a target nozzle row corresponding pattern 214. However, in this example, the number of unit patterns 202 constituting the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 differs from that of the standard pattern. Figures 3(a) and 3(b) show an example of the configuration of the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 in the correction pattern of this example. In the correction pattern of this example, the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 are patterns in which five unit patterns 202 are arranged in the main scanning direction. The reference nozzle row corresponding pattern 212 is a pattern in which five unit patterns 202 are arranged in the main scanning direction without any gaps. The target nozzle row corresponding pattern 214 is a pattern in which five unit patterns 202 are arranged in the main scanning direction with a gap of one pixel between them. In other words, the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 in this example are patterns obtained by omitting the unit patterns 202 at both ends from the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 in the standard pattern shown in Figure 2. Therefore, if the correction pattern in this example is used simply in the same way as the standard pattern, the range of the amount of impact position deviation that can be identified will be narrower compared to the standard pattern. More specifically, if the amount of impact position deviation is +3 pixels or -3 pixels, the patch 220 corresponding to the peak patch in the standard pattern shown in Figure 2 will not exist in the correction pattern in this example. In other words, if the correction pattern in this example is used simply in the same way as the standard pattern, it will only be possible to identify the amount of impact position deviation in the range of -2 pixels to +2 pixels.

[0035] In contrast, the control unit 30 (see Figure 1) of the printing apparatus 10 in this example identifies the impact position deviation in the range of -3 pixels to +3 pixels, based on the correction pattern shown in Figure 3, similar to the case where a standard pattern with seven patches 220 arranged in a row is used, for example, as shown in Figure 3(c). Figure 3(c) shows an example of the operation to identify the amount of impact position deviation using the correction pattern in this example. The three upper figures in Figure 3(c) show an example of the operation to identify the amount of impact position deviation when the amount of impact position deviation is between -2 pixels and +2 pixels. In this case, the control unit 30 identifies the amount of impact position deviation in the same way as when using the standard pattern. Specifically, the control unit 30 identifies the position of the patch 220 with the largest amount of reflected light based on the detection result of reflected light by the optical sensor 104 (see Figure 1), and identifies the amount of impact position deviation.

[0036] The two lower figures in Figure 3(c) show examples where the impact position deviation is -3 pixels and +3 pixels. As mentioned above, in this case, the correction pattern in this example does not include the peak patch in the standard pattern. However, in this case, as shown in the figure, of the five patches 220, the second patch 220 from the right or left has the element pattern 200 of the target nozzle row corresponding pattern 214 inserted into the gap of the element pattern 200 of the reference nozzle row corresponding pattern 212 (see Figure 2). As a result, the amount of reflected light is minimized at the position of this patch 220. If we define the patch 220 where the amount of reflected light is minimized as the bottom patch, then in the case where the impact position deviation is -3 pixels or +3 pixels, the bottom patch does not become the edge patch, and the amount of reflected light decreases monotonically as you approach the bottom patch on both sides. Also, when using the standard pattern or the correction pattern in this example, the bottom patch is the patch 220 located a predetermined number of pixels away from the peak patch. Specifically, in the patterns shown in Figures 2 and 3, patch 220 located four pixels away from the peak patch becomes the bottom patch. Therefore, when using the correction pattern in this example, even if the peak patch does not appear, the position of the original peak patch can be estimated as long as the bottom patch exists. For example, in the two lower figures in Figure 3(c), based on the position of the bottom patch indicated by the letter "Bottom" in the figure, it can be estimated that the position indicated as the estimated Peak position in the figure is the original peak patch position. This allows for the identification of a deviation in the impact position within the range of -3 pixels to +3 pixels, similar to when using the standard pattern with seven patches 220 arranged in a row. In this way, by using the correction pattern in this example, the amount of deviation in the impact position can be appropriately identified while reducing the drawing area required for printing the correction pattern.

[0037] Here, the correction pattern in this example may have a different number of patches 220 than five, or a different arrangement of them than described above. In this case as well, the specific configurations of the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 should be adjusted according to the number and arrangement of patches 220. In other words, the correction pattern in this example is a pattern in which the patch that produces the maximum or minimum amount of reflected light changes according to the actual amount of displacement, and includes 2N+1 patches 220 corresponding to displacement amounts of -N pixels (where N is an integer of 1 or more) and +N pixels. The correction pattern including the five patches 220 described above is the pattern corresponding to the case where N=2.

[0038] Thus, in the correction pattern, the patch 220 that serves as a reference for indicating the amount of deviation in the point of impact may be a peak patch (the patch 220 where the amount of reflected light is maximum) or a bottom patch (the patch 220 where the amount of reflected light is minimum). One of these peak and bottom patches is called the first pole state, and the other is called the second pole state. In the example shown in Figure 3, the state of reflected light occurring at the peak patch is the first pole state, and the state of reflected light occurring at the bottom patch is the second pole state. Here, if the reflected light is maximum or minimum at the position of the outermost patch 220 in the arrangement of patches 220, it is not determined to be a maximum or minimum. In other words, the first pole state and the second pole state referred to here are states in which the amount of reflected light is maximum or minimum at the positions of patches 220 other than the outermost patch 220.

[0039] For example, as shown in the top diagram of Figure 3(c), if any of the patches 220 become a peak patch, the amount of reflected light from that patch 220 reaches the first pole state. The control unit 30 uses the amount of displacement corresponding to the patch 320 that has reached the first pole state as the detected displacement amount. The detected displacement amount is the amount of displacement of the impact position that the control unit 30 identifies based on the reflected light detected by the optical sensor 104. The control unit 30 corrects the impact position based on the detected displacement amount. Here, in the case of the diagram corresponding to -2 pixels or +2 pixels in Figure 3(c), the outermost patch 320 becomes the peak patch, so the amount of reflected light from this peak patch is not determined to be at its maximum. As a result, the amount of reflected light from any of the patches 220 does not reach the first pole state, and the amount of reflected light increases or decreases monotonically. In this case, the control unit 30 uses -N pixels or +N pixels as the detected displacement amount, depending on how the amount of reflected light changes. Similarly, if the actual displacement of the impact position is greater than the displacement assumed by the correction pattern, the amount of reflected light may monotonically increase or decrease. In this case, the larger displacement of the impact position causes the overall width of the correction pattern in the main scanning direction to become larger than usual. Therefore, in this case, it can be determined that a displacement has occurred that does not fall within the range of -N pixels to +N pixels, based on the overall width of the correction pattern.

[0040] Furthermore, in the case of the diagram corresponding to the displacement of the impact position of the -3 pixels in Figure 3(c), the amount of reflected light from any patch 220 does not reach the first pole state, and the amount of reflected light from patch 220 that becomes the peak patch with a displacement of +(N-1) pixels is in the second pole state. In this case, the control unit 30 estimates the position shown as the Peak estimated position in the diagram as the position of the original peak patch, and uses the displacement of the -(N+1) pixels as the detected displacement amount. Furthermore, in the case of the diagram corresponding to the displacement of the impact position of the +3 pixels in Figure 3(c), the amount of reflected light from any patch 220 does not reach the first pole state, and the amount of reflected light from patch 220 that becomes the peak patch with a displacement of -(N-1) pixels is in the second pole state. In this case, the control unit 30 estimates the position shown as the Peak estimated position in the diagram as the position of the original peak patch, and uses the displacement of the +(N+1) pixels as the detected displacement amount. This configuration reduces the area required for printing the correction pattern, as well as the amount of media and ink consumed for correcting the impact position, thereby shortening the time required for printing the correction pattern and identifying the amount of misalignment.

[0041] In this example, the control unit 30 corrects the impact position by adjusting the timing of ink ejection from the nozzle row based on the result of identifying the amount of deviation in the impact position. The control unit 30 corrects the impact position of the target nozzle row by adjusting the timing of ink ejection from the nozzles of the target nozzle row, using the timing of ink ejection from the nozzles of the reference nozzle row as a reference. As described above, the reference nozzle row in this example is an example of the first nozzle row. The target nozzle row is an example of the second nozzle row. In this example, the operation by which the control unit 30 corrects the impact position is an operation in which the impact position of one of the first nozzle row and the second nozzle row is used as a reference and the impact position of the other nozzle row is corrected based on the amount of deviation in the impact position identified using the optical sensor 104.

[0042] In this example, the target nozzle row is a different nozzle row from the reference nozzle row. In other words, the impact position correction performed by the control unit 30 is a correction of the impact position between multiple nozzle rows. The target nozzle row may also be a nozzle row of an inkjet head different from the inkjet head having the reference nozzle row. In this case, the impact position correction performed by the control unit 30 can also be considered as a correction of the impact position between multiple inkjet heads. Furthermore, the main scanning drive unit 18 (see Figure 1) of the printing device 10 may cause the head unit 12 (see Figure 1) to perform the reciprocating main scanning operation. In this case, a discrepancy may occur between the impact position in the main scanning operation in the forward direction of a single nozzle row and the impact position in the main scanning operation in the return direction. Therefore, when correcting the impact position between multiple nozzle rows or between multiple inkjet heads in this example, the control unit 30 performs the correction by making the direction of movement of the head unit 12 the same. Separately, when the printing apparatus 10 has the head unit 12 perform a reciprocating main scanning operation, it is preferable to perform a correction to reduce the discrepancy between the impact position in the forward main scanning operation and the impact position in the return main scanning operation for one nozzle row. In this case, the control unit 30 uses the same nozzle row as the reference nozzle row as the target nozzle row, ejects ink from the nozzle row of the reference nozzle row in one main scanning operation in either the forward or return direction, and ejects ink from the nozzle row of the target nozzle row in the other main scanning operation. With this configuration, the impact position in the reciprocating main scanning operation can be corrected using the correction pattern of this example, similar to the operation described above.

[0043] As described above, the printing apparatus 10 of the present example is a flatbed inkjet printer. In a flatbed inkjet printer, a difference may occur in the deviation amount of the landing position depending on the position of the medium. The entire medium is placed on the upper surface of the table 14 (see FIG. 1) of the present example. Further, the head unit 12 is supported by the Y bar 16 (see FIG. 1) so as to face the medium. At this time, if the table 14 or the Y bar 16 has deflection or distortion, a slight difference occurs in the distance between the head unit 12 and the medium depending on the position on the table 14, and a difference also occurs in the deviation amount of the landing position. Accordingly, the control unit 30 of the present example corrects the landing position for each position at a plurality of locations on the medium. Such correction of the landing position associated with a local range on the medium is referred to as local correction. In the local correction, the control unit 30 prints correction patterns at a plurality of locations on the medium placed on the table 14, thereby identifying the deviation amount of the landing position for each position.

[0044] When performing such local correction, it is necessary to print a large number of correction patterns on the medium. In this case, by reducing the seven patches included in the standard pattern to five as in the correction pattern shown in FIG. 3, the drawing area required for printing one correction pattern is reduced. In addition, this makes it possible to divide the board surface of the table 14 into more fine regions and perform local correction.

[0045] Furthermore, when performing local correction, the amount of deviation in the impact position detected by the optical sensor 104 may also differ depending on the position on the table 14. In this case, the amount of deviation in the impact position occurring at the first position on the table 14 and the amount of deviation occurring at the second position should normally change gradually in proportion to the distance between the first and second positions. Therefore, the control unit 30 can detect abnormal values ​​in the amount of deviation by comparing the amount of deviation in the impact position detected at each position on the table 14 and detecting values ​​that deviate significantly from the detection results at other positions. Such differences in the amount of deviation in the impact position due to the position of the medium can also occur in printing devices 10 other than flatbed type. For example, even when using a vertical inkjet printer as the printing device 10, differences in the amount of deviation in the impact position may occur depending on the position during the main scanning operation. In such cases as well, it is preferable to perform local correction in the same manner as described above.

[0046] Furthermore, as described above, the print head 12 in this example ejects ink of multiple colors. Therefore, as shown in Figure 4(a), for example, it is necessary to correct for the misalignment of the impact positions that occurs between multiple nozzle rows ejecting different colors. Figure 4 is a diagram that further explains the correction of the impact positions performed in the printing apparatus 10 of this example. Except for the points described below, in Figure 4, components that are denoted by the same reference numerals as in Figures 2 and 3 can be considered to be the same or similar as the components in Figures 2 and 3. Also, in Figure 4 and the drawings described below, for the sake of illustration, differences in ink colors are represented by different shading patterns.

[0047] Figure 4(a) shows an example of a pattern used to correct the impact position for multiple nozzle rows that eject different colors. In the example in Figure 4(a), a reference nozzle row corresponding pattern 212 and a target nozzle row corresponding pattern 214 are used, similar to the standard pattern described using Figure 2. The pattern shown in Figure 4(a) is a pattern that corresponds to at least a part of the correction pattern. When printing this pattern, the control unit 30 (see Figure 1) uses one of the nozzle rows for the first color (e.g., black) as the reference nozzle row and ejects ink to the ejection position corresponding to the reference nozzle row corresponding pattern 212. The control unit 30 also uses a nozzle row for a second color (e.g., cyan) that is different from the first color as the target nozzle row and ejects ink to the ejection position corresponding to the target nozzle row corresponding pattern 214. In this way, the control unit 30 causes the head unit 12 (see Figure 1) to print a correction pattern consisting of multiple patches 220 by superimposing the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214, for example, as shown in the lower part of Figure 4(a).

[0048] Also, in FIG. 4(a), for convenience of illustration, only the part corresponding to one nozzle row for the second color in the correction pattern is shown. However, when a plurality of nozzle rows for the second color ink are present in the head unit 12, the control unit 30 causes the head unit 12 to print a pattern similar to the pattern shown in the drawing for each nozzle row of the second color. In this case, the control unit 30 fixes the nozzle row used as the reference nozzle row, sequentially selects one nozzle row from the plurality of nozzle rows for the second color as the target nozzle row, and causes the head unit 12 to print 7 patches 220 for each of the nozzle rows for the second color. Therefore, for example, when using the printing apparatus 10 having a configuration in which the first color is black, the second color is cyan, and there are four nozzle rows for the same color as in the configuration described with reference to FIG. 1, a total of 28 patches need to be printed in order to correct the landing position between any one of the black nozzle rows and the plurality of cyan nozzle rows. Further, as described above, the head unit 12 of the present example similarly has a plurality of nozzle rows for yellow, magenta, and the like. Therefore, in order to correct the landing positions for these color nozzle rows, it is necessary to further print the same number of patches. Even in this case, the required number of patches can be reduced by using, for example, the correction pattern described with reference to FIG. Specifically, by reducing the number of patches corresponding to one nozzle row for the second ink to 5, the number of patches 220, which was 28, can be reduced to 20.

[0049] In the printing apparatus 10 of this example, the amount of reflected light generated by peak patches and bottom patches under ideal conditions is used to further enable correction of the impact position with a smaller number of patches 220. Figure 4(b) shows an example of a normal peak patch and bottom patch. The peak patch is the patch with the maximum amount of reflected light among the seven patches 220 arranged in the lower part of Figure 4(a). In the peak patch, for example, as shown in the left part of Figure 4(b), the unit pattern 202 of the reference nozzle row corresponding pattern 212 and the unit pattern 202 of the target nozzle row corresponding pattern 214 are aligned and overlap, increasing the area of ​​the part not covered by ink. As a result, for example, when using a pattern in which multiple patches 220 are arranged as shown in the lower part of Figure 4(a), the amount of reflected light from the position of the peak patch is the maximum among the multiple patches 220. In contrast, in the bottom patch, as shown in the right-hand diagram in Figure 4(b), for example, the position of the unit pattern 202 of the reference nozzle row corresponding pattern 212 and the position of the unit pattern 202 of the target nozzle row corresponding pattern 214 are misaligned, resulting in a larger area covered by ink. As a result, the amount of reflected light from the bottom patch is the smallest among the multiple patches 220.

[0050] The displacement of the impact point between multiple nozzle rows typically occurs in fractional units of less than one pixel. Peak and bottom patches are usually not ideal due to the influence of the slight impact position between the multiple nozzle rows used to draw patch 220. In contrast, when ejecting ink with only one nozzle row, if the direction of movement of the head unit 12 during the main scanning operation is also kept the same, theoretically, the amount of impact point displacement can be brought as close to zero as possible. For example, if the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 are printed with the same nozzle while keeping the direction of movement of the head unit 12 constant during the main scanning operation, ideal or near-ideal peak and bottom patches can be printed, as shown in Figure 4(c). In this case, the control unit 30 prints the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 on the same nozzle row in different main scanning operations.

[0051] In the following, for the sake of explanation, the correction pattern described using Figure 5 will be referred to as the correction pattern of this example. Figure 5 is a diagram illustrating the characteristics of the correction pattern of this example. Figure 5(a) shows an example of the configuration of the unit pattern 302 used in the correction pattern of this example. As shown in the figure, the unit pattern 302 is a pattern in which multiple rectangular element patterns 300, with the sub-scanning direction as the longitudinal direction, are arranged in the main scan direction. Except for the points described below, the unit pattern 302 and the element patterns 300 in the unit pattern 302 may have the same characteristics as the unit pattern 202 and element patterns 200 (see Figure 2) described above using Figure 2. In the unit pattern 302 shown in Figure 5(a), the width of the element patterns 300 and the width of the gaps between the element patterns 300 are different from the width of the unit pattern 202 in Figure 2. The unit pattern 202 shown in Figure 2 is a pattern in which 4-pixel wide element patterns 200 and 4-pixel blank spaces are arranged alternately. In contrast, the width of the element pattern 300 in the main scanning direction of the unit pattern 302 in Figure 5(a) is the width of 6 pixels. Also, the width of the gaps between the element patterns 300 is the width of 6 pixels.

[0052] In this regard, the difference in width between the element pattern 300 in unit pattern 302 and the element pattern 200 in unit pattern 202 corresponds to the difference between cases where the amount of reflected light intensity changes depending on the direction of the shift, and cases where it does not change, with respect to the change in the amount of shift in the impact position at the position of the patch used in the correction pattern. Specifically, in the case of the correction pattern using unit pattern 202 in Figure 2, with respect to the shift in the range of -3 pixels to +3 pixels, the amount of reflected light intensity changes according to the absolute value of the magnitude of the shift, regardless of the direction of the shift. Therefore, by further determining the position of the patch that becomes the peak patch, it is possible to determine whether the impact position is shifted in the negative or positive direction. For this reason, in this case, with N as an integer of 1 or more, the width of the element pattern 200 in the main scanning direction is N+1 pixels in order to specify the shift in the range of -N pixels to +N pixels.

[0053] In contrast, the unit pattern 302, as will be explained below using Figure 5(b) for example, exhibits differences in the amount of reflected light when the direction of the shift is different, even if the absolute value of the shift is the same, with respect to a shift in the range of -3 pixels to +3 pixels. Figure 5(b) shows an example of the change in the amount of reflected light that occurs in a patch using the unit pattern 302 according to the amount of shift in the impact position. The pattern shown in Figure 5(b) is a reference pattern for explaining the characteristics of the correction pattern in this example. In this reference pattern, for example, as shown in the figure, a reference nozzle row corresponding pattern 312 drawn using a reference nozzle row and a target nozzle row corresponding pattern 314 drawn using a target nozzle row are used. The reference nozzle row corresponding pattern 312 is a pattern in which seven unit patterns 302 are arranged in the main scanning direction without any gaps, similar to the reference nozzle row corresponding pattern 212 in Figure 2 (see Figure 2). Furthermore, the target nozzle row corresponding pattern 314 is a pattern in which seven unit patterns 302 are arranged in the main scanning direction with a gap of one pixel between them, similar to the target nozzle row corresponding pattern 314 in Figure 2 (see Figure 2).

[0054] In this reference pattern, the way in which the reference nozzle row corresponding pattern 312 and the target nozzle row corresponding pattern 314 are superimposed differs from the way in which the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 are superimposed in Figure 2. As described above, in the case of the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 in Figure 2, the reference nozzle row corresponding pattern 212 and the target nozzle row corresponding pattern 214 are superimposed so that, in the ideal state, the positions of the unit pattern 202 of the reference nozzle row corresponding pattern 212 and the unit pattern 202 of the target nozzle row corresponding pattern 214 are aligned at the position of the central patch 220 (see Figure 2). In contrast, in the case of this example pattern, as shown in the lower part of Figure 5(b), in the ideal state, the reference nozzle row corresponding pattern 312 and the target nozzle row corresponding pattern 314 are superimposed such that the positions of the unit pattern 302 of the reference nozzle row corresponding pattern 312 and the unit pattern 302 of the target nozzle row corresponding pattern 314 are aligned at the position of patch 320 at one end in the main scanning direction. The ideal state here refers to a state in which there is no difference in the impact position (impact error) between the reference nozzle row and the target nozzle row. Furthermore, as mentioned above, such an ideal state can be considered the same state as when the reference nozzle row corresponding pattern 312 and the target nozzle row corresponding pattern 314 are drawn with the same nozzle row. In Figure 5(b), as an example of this ideal state, an example is shown in which the cyan nozzle row of the head 1 of the head unit 12 is used for both the reference nozzle row and the target nozzle row.

[0055] In the illustrated example, the reference nozzle row corresponding pattern 312 and the target nozzle row corresponding pattern 314 are superimposed so that the unit pattern 302 of the reference nozzle row corresponding pattern 312 and the unit pattern 302 of the target nozzle row corresponding pattern 314 are aligned at the position of the leftmost patch 320 in the figure. In this case, the central patch 320, labeled "Center" in the figure, has the unit patterns 302 of each nozzle row drawn with a shift of +3 pixels, which represents a state where the amount of impact position shift is 0 (a state where the impact error is 0 pixels). With Center as the reference, the patch 320 whose impact position is shifted by -3 pixels from Center (a state where the impact error is -3 pixels) becomes the peak patch, and the patch 320 whose impact position is shifted by +3 pixels (a state where the impact error is +3 pixels) becomes the bottom patch. Also, as shown in the figure, the areas covered by ink for these seven patches 320 are different from each other. As a result, within the range of -3 pixels to +3 pixels, the amount of reflected light from the position of patch 320 will differ in seven ways. Therefore, with this configuration, it is possible to identify not only the absolute value of the shift but also the direction of the shift based on the amount of reflected light. In this case, it can be considered that the amount of reflected light obtained from the seven patches 320 covers the seven possible amounts of light that appear in the range of -3 pixels to +3 pixels. In the ideal arrangement of these seven patches 320, the ideal peak patch and the ideal bottom patch are located at the left and right ends, and the ideal center patch, which corresponds to an intermediate state, is in the center. The ideal center patch is a patch 320 in which the unit pattern 302 of the reference nozzle row corresponding pattern 312 and the unit pattern 302 of the target nozzle row corresponding pattern 314 are shifted by 3 pixels in the main scanning direction. Furthermore, in order to identify the shift in the range of -N pixels to +N pixels, it can be considered that the width of the element pattern 300 in the main scanning direction is 2N pixels.

[0056] When actually determining the amount of deviation in the impact position, different nozzle rows are used as the reference nozzle row and the target nozzle row. In this case, using the reference nozzle row corresponding pattern 312 and the target nozzle row corresponding pattern 314 shown in Figure 5(b), if the reference nozzle row corresponding pattern 312 drawn with the reference nozzle row and the target nozzle row corresponding pattern 314 drawn with the target nozzle row are superimposed, the result may differ from the lower state in Figure 5(b), as shown in Figure 5(c). Figure 5(c) shows an example of the change that occurs depending on the amount of deviation in the impact position between the reference nozzle row and the target nozzle row when the cyan nozzle row of head 1 in the head unit 12 is used as the reference nozzle row and the cyan nozzle rows of heads 2 to 4 are used as the target nozzle row. The upper part of Figure 5(c) shows an example when the amount of deviation in the impact position (impact error) is 0 pixels when the cyan nozzle row of head 2 is used as the target nozzle row. The central diagram in the vertical direction of the figure shows an example where the cyan nozzle row of head 3 is used as the target nozzle row, and the displacement of the impact position is -1 pixel. The lower diagram shows an example where the cyan nozzle row of head 4 is used as the target nozzle row, and the displacement of the impact position is +2 pixels. As can be seen from these examples, the patch 320 that becomes the peak patch or bottom patch changes depending on the amount of displacement of the impact position. Also, as shown in the central and lower diagrams of Figure 5(c), for example, there are cases where either the peak patch or the bottom patch does not exist.

[0057] Furthermore, in this case, as the peak and bottom patches 320 change, the amount of reflected light detected by the optical sensor 104 (see Figure 1) at the center patch, which is the central patch 320, also changes. The amount of reflected light detected at the center patch is close to the amount of reflected light obtained at any patch 320 position in the ideal state shown in Figure 5(b), depending on the amount of displacement of the impact position between the reference nozzle row and the target nozzle row. Therefore, by using this relationship, the amount of displacement of the impact position can be identified by determining which patch 320 position in the ideal arrangement of patches 320 the amount of reflected light detected at the center patch is close to. However, even in this case, if a large number of patches 320 (for example, 7 patches 320) are used for each target nozzle row, the production area required for printing the correction pattern increases. Therefore, in the correction pattern of this example, the required production area can be reduced by using a pattern with a configuration described below using, for example, Figure 6.

[0058] Figure 6 illustrates the features of the correction pattern in this example. Except for the points described below, components in Figure 6 that are denoted by the same reference numerals as in Figure 5 may be considered to be the same as or similar to the components in Figure 5. Figure 6(a) shows an example of a portion of the correction pattern in this example that corresponds to multiple nozzle rows for one color. Figure 6(a) is a part of the correction pattern and corresponds to the four cyan nozzle rows of heads 1 to 4 of the head unit 12 (see Figure 1). In this portion, the correction pattern in this example has a color-inter-adjustment pattern 332, a reference pattern 334, and multiple target patterns 336. The color-inter-adjustment pattern 332 is a pattern for identifying the amount of deviation in the impact position between nozzle rows of different colors by using nozzle rows of different colors as the reference nozzle row and the target nozzle row. As the color-inter-adjustment pattern 332, for example, the standard pattern described using Figure 2 can be suitably used. Alternatively, the correction pattern described using Figure 3 may be used as the color-inter-adjustment pattern 332. In contrast, the reference pattern 334 and the multiple target patterns 336 are patterns for determining the amount of deviation in the impact position between multiple nozzle rows of the same color.

[0059] With respect to these patterns, when adjusting the impact position using the correction pattern in this example, the printing device 10 (see Figure 1) corrects the impact position for all nozzle rows for all colors, using one of the nozzle rows for any of the multiple inks used by the head unit 12 as a reference. In this case, it is preferable to use, for example, the nozzle row for black ink as the reference nozzle row for all nozzle rows for all colors. In this example, the control unit 30 corrects the impact position between multiple nozzle rows for black ink using, for example, the standard pattern explained with reference to Figure 2 or the correction pattern explained with reference to Figure 3. Furthermore, the control unit 30 corrects the impact position for nozzle rows of other colors using, for example, the pattern shown in Figure 6(a) as a reference. Then, the control unit 30 uses the inter-color adjustment pattern 332 to identify the amount of deviation in the impact position corresponding to any nozzle row for any color other than black, using one of the nozzle rows for black ink as a reference.

[0060] In the example shown in Figure 6(a), the nozzle row for black color on head 1 is used as the reference nozzle row for drawing the color adjustment pattern 332. The nozzle row for cyan color on head 1 is used as the target nozzle row. In the correction pattern of this example, the target nozzle row corresponding to the color adjustment pattern 332 is used as the reference nozzle and target nozzle corresponding to the reference pattern 334, and further, it is used as the reference nozzle row corresponding to the target pattern 336. Specifically, in the example shown in Figure 6(a), the nozzle row for cyan color on head 1 is used as the reference nozzle and target nozzle corresponding to the reference pattern 334, and as the reference nozzle row corresponding to the target pattern 336. Furthermore, the target nozzle row corresponding to the target pattern 336 is a nozzle row for the same color as the reference nozzle row, and is the nozzle row that is the target of the impact position correction. A nozzle row different from the reference nozzle row is used as the target nozzle row corresponding to the target pattern 336. Furthermore, in the example shown in Figure 6(a), for each of the three target patterns 336, the nozzle rows for cyan color in each of the heads 2 to 4 are used as the target nozzle rows.

[0061] As can be understood from the configuration illustrated in Figure 6(a), the reference pattern 334 of the correction pattern in this example consists of fewer patches compared to the reference pattern with seven patches arranged at the bottom of Figure 5(b). Furthermore, the target pattern 336 corresponds to only one patch. Therefore, by using the correction pattern in this example, the production area required for printing the correction pattern can be reduced compared to when using the reference pattern shown in Figure 5(b). In addition, the reference pattern 334 in the correction pattern in this example is a pattern that includes at least patches corresponding to the ideal peak patch and the ideal bottom patch. Patches corresponding to the ideal peak patch and the ideal bottom patch are patches that are in the same state as the peak patch and bottom patch in the reference pattern of the ideal state. Furthermore, for the sake of convenience in explanation, in the following, patches corresponding to the ideal peak patch and the ideal bottom patch will simply be referred to as the ideal peak patch and the ideal bottom patch. In the example illustrated in Figure 6(a), the reference pattern 334 is a pattern composed only of patches corresponding to the ideal peak patch and the ideal bottom patch. This is drawn by superimposing, for example, the reference nozzle row corresponding pattern 312 and the target nozzle row corresponding pattern 314 shown in Figure 6(b). Figure 6(b) shows an example of the configuration of the reference pattern 334. The left side of the figure shows an example of the configuration of the reference nozzle row corresponding pattern 312 and the target nozzle row corresponding pattern 314 corresponding to the reference pattern 334. In the illustrated example, the reference nozzle row corresponding pattern 312 is a pattern in which two unit patterns 302 are arranged in the main scanning direction without any gaps. The target nozzle row corresponding pattern 314 is a pattern in which two unit patterns 302 are arranged in the main scanning direction with a gap of 6 pixels between them. The unit patterns 302 of the reference nozzle row corresponding pattern 312 and the target nozzle row corresponding pattern 314 are the patterns explained using Figure 5(a).When the positions of the unit patterns 302 on one side (for example, the left side in the figure) of the reference nozzle row corresponding pattern 312 and the target nozzle row corresponding pattern 314 are aligned and the reference nozzle row corresponding pattern 312 and the target nozzle row corresponding pattern 314 are superimposed, as shown in the right-hand figure of Figure 6(b), for example, one patch 320 corresponding to one unit pattern 302 becomes the peak patch, and the other patch 320 corresponding to the other unit pattern 302 becomes the bottom patch. The peak patch and bottom patch in the reference pattern 334 can be considered to be the ideal peak patch and ideal bottom patch drawn with only one nozzle row.

[0062] The peak patch of the reference pattern 334 is a patch where the positional shift between the unit pattern 302 corresponding to the reference nozzle row and the unit pattern 302 corresponding to the target nozzle row is 0 pixels. The amount of reflected light generated at the position of this peak patch corresponds to the amount of reflected light from the position of patch 320 (the leftmost patch 320 in the figure) which corresponds to a -3 pixel shift in the impact position in the ideal state reference pattern shown in Figure 5(b). The bottom patch of the reference pattern 334 is a patch where the positional shift between the unit pattern 302 corresponding to the reference nozzle row and the unit pattern 302 corresponding to the target nozzle row is +6 pixels. The amount of reflected light generated at the position of this bottom patch corresponds to the amount of reflected light from the position of patch 320 (the rightmost patch 320 in the figure) which corresponds to a +3 pixel shift in the impact position in the ideal state reference pattern shown in Figure 5(b). By including such peak and bottom patches, the reference pattern 334 represents a reference state for measuring the amount of impact position shift. The reference pattern 334 is drawn using only one of the reference nozzle rows in the head unit 12, thereby serving as a reference for measuring the amount of deviation in the impact position. Furthermore, as explained in relation to the ideal peak patch shown in Figure 4(c), in the correction pattern of this example, the control unit 30 makes the main scanning operation performed by the head unit 12 to draw the reference nozzle row corresponding pattern 312 and the main scanning operation performed by the head unit 12 to draw the target nozzle row corresponding pattern 314 different when printing the reference pattern 334.

[0063] Furthermore, the target pattern 336 in the correction pattern of this example is the pattern corresponding to the center patch in Figure 5(c). The correction pattern of this example uses multiple target patterns 336 corresponding to each nozzle row other than the one nozzle row used as the reference nozzle row among the multiple nozzle rows for one color in the head unit 12. Therefore, the number of target patterns 336 is one less than the number of multiple nozzle rows for one color in the head unit 12. In the example of Figure 6(a), the correction pattern has three target patterns 336 for one color. These target patterns 336 include the pattern corresponding to the center patch of the pattern when the cyan nozzle rows of heads 2 to 4 are used as the target nozzle rows, as shown in Figure 5(c).

[0064] In the correction pattern of this example, the patch included in the target pattern 336 is a pattern formed by superimposing a unit pattern 302 drawn with the reference nozzle row and a unit pattern 302 drawn with the target nozzle row. In other words, the target pattern 336 is a pattern that includes patches drawn using multiple (two) nozzle rows, including the target nozzle row. The unit pattern 302 drawn with the reference nozzle row is an example of the reference nozzle row corresponding part, which is the part drawn using the reference nozzle row. The unit pattern 302 drawn with the target nozzle row is an example of the target nozzle row corresponding part, which is the part drawn using the target nozzle row. As the reference nozzle row corresponding part and the target nozzle row corresponding part overlap in the patch included in the target pattern 336, the amount of reflected light changes according to the amount of displacement of the impact position between the reference nozzle row and the target nozzle row.

[0065] For example, when using the pattern shown in Figure 5(c), the amount of reflected light detected at the center patch will be close to the amount of light from one of the patches in the ideal state shown in Figure 5(b), depending on the amount of deviation in the impact position. Therefore, by determining which patch 320 in the ideal state the amount of reflected light detected at the center patch is closest to, the amount of deviation in the impact position can be identified. Thus, by using the center patch example in Figure 5(c) for the target pattern 336 in this example, the production area required for printing the correction pattern can be significantly reduced.

[0066] In this example, the reference pattern 334 in the correction pattern is used for the same purpose as the reference pattern of the ideal state shown in Figure 5(b). The reference pattern of the ideal state shown in Figure 5(b) includes multiple patches 320 for comparing the amount of reflected light and the amount of reflection detected at the position of the center patch. In contrast, the reference pattern 334 in the correction pattern of this example includes only the ideal peak patch and the ideal bottom patch. However, even when using this reference pattern 334, the amount of deviation in the impact position can be determined based on the amount of reflected light from the target pattern 336.

[0067] In this regard, the amount of reflected light from the position of one target pattern 336 corresponding to the center patch in Figure 5(c) is within the range between the amount of reflected light corresponding to the ideal peak patch and the amount of reflected light corresponding to the ideal bottom patch. Then, by interpolating using pre-prepared mathematical formulas, the amount of reflected light from the positions of patches 320 other than the peak patch and bottom patch in the reference pattern in the ideal state can be theoretically calculated. By comparing the theoretically calculated amount of light with the amount of light actually detected at the position of the target pattern 336, the amount of deviation in the impact position on the target pattern 336 can be determined. For example, by linear interpolation (linear approximation) between the amount of reflected light corresponding to the ideal peak patch and the amount of reflected light corresponding to the ideal bottom patch, the amount of deviation in the impact position on the target pattern 336 can be determined. In this case, it becomes possible to specify the amount of deviation in the impact position in detail to decimal units.

[0068] More specifically, when using the correction pattern configuration shown in Figure 6(a), if we focus on one of the target patterns 336 and let Δy be the amount of shift in the impact position between the reference nozzle row and the target nozzle row corresponding to that target pattern 336, then the amount of reflected light detected at the position of this target pattern 336, which is the patch reflected light amount, can be calculated using the following formula, where the amount of reflected light from the position of the ideal peak patch is the ideal peak patch reflected light amount, and the amount of reflected light from the position of the ideal bottom patch is the ideal bottom patch reflected light amount: Patch reflected light amount = (Ideal peak patch reflected light amount - Ideal bottom patch reflected light amount) x (3 - Δy) / 6 + Ideal bottom patch reflected light amount The amount of shift in the impact position Δy can then be calculated from the reflected light amount using the following formula: Δy = 3 - 6 x (Patch reflected light amount - Ideal bottom patch reflected light amount) / (Ideal peak patch reflected light amount - Ideal bottom patch reflected light amount)

[0069] In this regard, among the target patterns 336 shown in Figure 6(a), the target pattern 336 on the left is a pattern in which the nozzle row for cyan color of head 2 is used as the target nozzle row, and there is no shift in the point of impact between the reference nozzle row and the target nozzle row. In this case, theoretically, the amount of reflected light from the position of this target pattern 336 will be the same as the amount of reflected light from the center patch (ideal center patch) in the reference pattern in the ideal state. Also, in relation to the above formula, the amount of reflected light from the position of this target pattern 336 is given by Δy = 0 as follows: Amount of reflected light = (Ideal peak patch reflected light amount - Ideal bottom patch reflected light amount) x 3 / 6 + Ideal bottom patch reflected light amount

[0070] Furthermore, the central target pattern 336 in the figure is a pattern where the nozzle row for cyan color of head 3 is used as the target nozzle row, and the difference in the point of impact between the reference nozzle row and the target nozzle row is -1 pixel. In this case, theoretically, the amount of reflected light from the position of this target pattern 336 will be the same as the amount of light at the position of patch 320, which corresponds to a -1 pixel difference in the ideal reference pattern. In this case, in relation to the above formula, the amount of reflected light from the position of this target pattern 336 will be as follows, with Δy = -1: Amount of reflected light = (Ideal peak patch reflected light amount - Ideal bottom patch reflected light amount) x 4 / 6 + Ideal bottom patch reflected light amount

[0071] Furthermore, the target pattern 336 on the right side of the figure is a pattern where the nozzle row for cyan color of head 4 is used as the target nozzle row, and the amount of displacement of the impact position between the reference nozzle row and the target nozzle row is +2 pixels. In this case, theoretically, the amount of reflected light from the position of this target pattern 336 will be the same as the amount of light at the position of patch 320 corresponding to the +2 pixel displacement in the reference pattern in the ideal state. Also, in relation to the above formula, the amount of reflected light from the position of this target pattern 336 is given by Δy = +2 as follows: Amount of reflected light = (Ideal peak patch reflected light amount - Ideal bottom patch reflected light amount) x 1 / 6 + Ideal bottom patch reflected light amount

[0072] As described above, in the correction pattern of this example, by using the reference pattern 334 and the target pattern 336, it is possible to detect the amount of deviation in the impact position between multiple nozzle rows for the same color. Furthermore, by using the inter-color adjustment pattern 332, it is also possible to identify the amount of deviation in the impact position of these multiple nozzle rows compared to the reference nozzle row of other colors. More specifically, by using the inter-color adjustment pattern 332, with respect to the nozzle rows of heads 1 to 4 of the head unit 12, it is possible to identify the amount of deviation in the impact position of the cyan nozzle row of head 1 relative to the black nozzle row 122 of head 1. In addition, by using the reference pattern 334 and the multiple target patterns 336, it is possible to identify the amount of deviation in the impact position of the cyan nozzle rows of heads 2 to 4 relative to the cyan nozzle row 122 of head 1. Then, by combining these detection results, it is possible to identify the amount of deviation in the impact position of the cyan nozzle rows of heads 1 to 4 relative to the black nozzle row 122 of head 1. Furthermore, as described above, the head unit 12 in this example further has nozzle rows for colors other than black and cyan. Similarly, the amount of deviation of the impact position relative to the black nozzle row 122 of the head 1 can be determined for the nozzle rows for the other colors as well.

[0073] Furthermore, in the operation described above, the control unit 30 determines the amount of deviation in the impact position by determining the amount of deviation through a predetermined calculation. The control unit 30 determines the amount of deviation in the impact position occurring between the reference nozzle row and the target nozzle row from the amount of reflected light from the positions of multiple patches in the reference pattern 334 and the amount of reflected light from the positions of patches in the target pattern 336. The control unit 30 also corrects the impact position based on the determined amount of deviation in the impact position. As described above, the number of patches included in one target pattern 336 may be one. With this configuration, the number of patches required for correcting the impact position can be significantly reduced. Therefore, according to this example, the production area required for printing the correction pattern can be reduced. In addition, this makes it possible to reduce the amount of media and ink consumed for correcting the impact position, and to shorten the time required for printing the correction pattern and detecting the amount of deviation.

[0074] For example, in the reference pattern explained using Figures 5(b) and 5(c), seven patches are required for each of the four nozzle rows, resulting in a total of 28 patches. In contrast, in the example shown in Figure 6(a), seven patches are required for one color adjustment pattern 332, two patches for one reference pattern 334, and three patches for three target patterns 336, resulting in a total of 12 patches.

[0075] Furthermore, as described above, the amount of reflected light from the patch position in the target pattern 336 changes according to the amount of displacement of the impact position between the reference nozzle row and the target nozzle row. In this case, the amount of reflected light from the patch position in the target pattern 336 can be defined as the maximum reflected light amount, the maximum amount of light that occurs within a preset range of impact position displacement, and the minimum amount of light that occurs. The ideal peak patch in the reference pattern 334 is an example of a maximum reflected light amount corresponding patch, which is the patch that corresponds to the maximum reflected light amount. The ideal bottom patch is an example of a minimum reflected light amount corresponding patch, which is the patch that corresponds to the minimum reflected light amount.

[0076] Here, it might seem that the amount of reflected light corresponding to the ideal peak patch and ideal bottom patch could be measured in advance during the manufacturing of the printing device 10, rather than drawing the reference pattern 334 within the correction pattern. However, when detecting the amount of reflected light from the patch position using the light sensor 104 (see Figure 1), the detection result may be affected by, for example, ambient light. Furthermore, the amount of reflected light may also change depending on the characteristics of the medium used (for example, the color of the medium). In contrast, in the case of the correction pattern in this example, by printing the reference pattern 334 together with the target pattern 336 onto the medium, the amount of reflected light from the ideal peak patch and ideal bottom patch can be obtained while reflecting the environment in which the target pattern 336 is drawn and the characteristics of the medium. As a result, even when using a target pattern 336 that contains only one patch, the amount of deviation of the target nozzle row's impact position can be appropriately determined based on the amount of reflected light from the target pattern 336. Furthermore, even when using the correction pattern in this example, the control unit 30 performs local correction to correct the impact position for each position by printing the correction pattern at multiple positions on the medium on the table 14 (see Figure 1). In this case, it is conceivable that differences in the influence of ambient light may occur depending on the position on the table 14. However, even in this case, since the correction pattern printed at each position has a reference pattern 334, the impact position at each position can be appropriately corrected even if there are differences in the influence of ambient light depending on the position. In this case as well, it is preferable that the control unit 30 detects abnormal values ​​included in the detection results based on the detection results of the amount of deviation corresponding to multiple positions on the table 14.

[0077] Furthermore, depending on the accuracy required for correcting the impact position, the reference pattern 334 may include patches other than the ideal peak patch and the ideal bottom patch, for example, as shown in Figure 6(c). Figure 6(c) shows another example of patches included in the reference pattern 334. In addition to the ideal peak patch and the ideal bottom patch, the reference pattern 334 further includes an intermediate patch, which is a patch 320 corresponding to the center patch (ideal center patch) in the reference pattern of the ideal state shown in Figure 5(b). The characteristics of the intermediate patch can be considered, for example, by focusing on the relationship with the minimum reflected light amount and the maximum reflected light amount described above. In this case, the intermediate patch can be considered an intermediate reflected light amount corresponding patch, which is a patch corresponding to a light amount that is greater than the minimum reflected light amount and less than the maximum reflected light amount. Also, when using the unit pattern 302 with the configuration shown in Figure 5(a), the intermediate patch is a pattern obtained by overlapping the unit pattern 302 corresponding to the reference nozzle row and the unit pattern 302 corresponding to the target nozzle row, shifted by +3 pixels in the main scanning direction.

[0078] In this case, the control unit 30 calculates (detects) the amount of deviation in the impact position corresponding to the target pattern 336 by linearly interpolating (linear approximation) the amount of reflected light between the ideal peak patch and the intermediate patch, and between the intermediate patch and the ideal bottom patch. The reference pattern 334 may also include patches other than the intermediate patch. For example, the same pattern as the reference pattern for the ideal state may be used as the reference pattern 334. Furthermore, depending on the accuracy required for correcting the impact position, the number of patches included in one target pattern 336 may be two or more. In this case, the target pattern 336 further includes patches corresponding to predetermined patches other than the center patch in the reference pattern for one target nozzle row.

[0079] Furthermore, considering the characteristics of the correction pattern in this example in a more generalized manner, as described above, the element pattern 300 in the unit pattern 302 has a width of 2N pixels (where N is an integer greater than or equal to 1) in the main scanning direction in order to detect a shift in the range of -N pixels to +N pixels. The unit pattern 302 is a pattern in which a predetermined number of element patterns 300, each with a width of 2N pixels in the main scanning direction, are arranged with a gap of 2N pixels between them. In addition, in the correction pattern in this example, the patches of the reference pattern 334 and the target pattern 336 are patterns in which two unit patterns 302 are superimposed with their positions aligned at least in the sub-scanning direction. Furthermore, the patch of the target pattern 336 is a pattern in which the unit pattern 302 drawn using the reference nozzle row and the unit pattern 302 drawn using the target nozzle row are superimposed with their positions shifted by N pixels in the main scanning direction. Furthermore, the patch of the reference pattern 334 can be considered as a pattern in which a first unit pattern 302 drawn using a reference nozzle row and a second unit pattern 302 drawn using a reference nozzle row overlap. In this case, the ideal peak patch in the reference pattern 334 can be considered as a first patch in which the first unit pattern 302 and the second unit pattern 302 are superimposed with their positions aligned in the main scanning direction. Also, the ideal bottom patch in the reference pattern 334 can be considered as a second patch in which the first unit pattern 302 and the second unit pattern 302 are superimposed with their positions shifted by 2N pixels in the main scanning direction.

[0080] Furthermore, in this example, the printing apparatus 10 corrects the ink impact position by adjusting the ejection timing of the nozzle row using the control unit 30, regardless of which correction pattern is used. The control unit 30 is an example of a control device that corrects the ink impact position for the printing apparatus 10. Depending on the configuration of the printing apparatus 10, it is also conceivable to use a control device located outside the printing apparatus 10 to correct the ink impact position for the printing apparatus. Such a control device could preferably be a computer that supplies print data to the printing apparatus 10.

[0081] Specifically, for example, a printing system 1000 with the configuration shown in Figure 7 could be used. Figure 7 shows an example of the configuration of the printing system 1000 when the impact position is corrected using a control device 1100 located outside the printing device 1200. The printing system 1000 is an example of a printing system composed of multiple devices. The printing system 1000 with the configuration shown in Figure 7 comprises a control device 1100 and a printing device 1200. The control device 1100 is, for example, a computer that executes a program to control at least a part of the operation of the printing device 1200, and executes at least a part of the functions of the control unit 30 (see Figure 1) of the printing device 10 described using Figures 1 to 6. Functionally, the control device 1100 has, for example, a printing control unit 1102, an impact position correction unit 1104, and a deviation amount calculation unit 1106, as shown in the figure. The printing control unit 1102 is configured to execute processing related to the control of the printing operation in the printing device 1200. The impact position correction unit 1104 is configured to perform the above-mentioned processing related to the correction of the impact position, and performs the processing related to the correction of the impact position based on the amount of deviation calculated by the deviation amount calculation unit 1106. The deviation amount calculation unit 1106 is configured to perform the above-mentioned processing related to the calculation of the deviation amount of the impact position.

[0082] Furthermore, the printing device 1200 of the printing system 1000 can also be considered as having the same configuration as the printing device 10 described with reference to Figures 1 to 6, but with the functions executed by the control device 1100 removed. In this case, the printing device 1200 has the same or similar configuration as the printing device 10, except for the part corresponding to the control unit 30 of the printing device 10. In this case, the printing device 1200 also has a control unit that performs processes other than those performed by the control device 1100, in the same way as the control unit 30 of the printing device 10. An example of such a control unit for the printing device 1200 is an ejection control unit that controls the ejection of ink to the print head.

[0083] Furthermore, the printing device 10 described above is an inkjet printer that draws a two-dimensional image on a medium. In a modified version of the printing device 10, it is also conceivable to use a 3D printer (3D printing device) that creates three-dimensional objects as the printing device 10. In this case, the build plate that supports the object being created and the object being created become the targets for ink ejection. In this case, when correcting the impact position, a medium such as paper or film is used as a temporary target for ink ejection. These printing devices 10 are examples of liquid ejection devices.

[0084] The present invention can be suitably used, for example, in printing systems and the like.

[0085] 10...Printing device, 100...Carriage, 102...Head row, 104...Optical sensor, 12...Head unit, 120...Inkjet head, 122...Nozzle row, 14...Table, 16...Y-bar, 18...Main scanning drive unit, 20...Sub-scanning drive unit, 200...Element pattern, 202...Unit pattern, 212...Reference nozzle row corresponding pattern, 214...Target nozzle row corresponding pattern, 220...Patch, 30...Control unit, 300...Element pattern, 302...Unit pattern, 312...Reference nozzle row corresponding pattern, 314...Target nozzle row corresponding pattern, 320...Patch, 332...Color interval adjustment pattern, 334...Reference pattern, 336...Target pattern, 50...Media, 1000...Printing system, 1100...Control device, 1200...Printing device, 1102...Printing control unit, 1104...Impact position correction unit, 1106...Shift amount calculation unit

Claims

1. A printing system that performs printing using an inkjet method, comprising: a head unit having a nozzle row in which a plurality of nozzles are arranged; a main scanning drive unit that causes the head unit to perform a main scanning operation in which ink is ejected while moving in the main scanning direction relative to the medium to which the ink is to be ejected; a light detection mechanism that detects reflected light from a correction pattern which is a pattern used to correct the deviation of the landing position of the ink ejected from the nozzles of the nozzle row; and a control unit that controls the operation of the head unit and the main scanning drive unit so as to cause the head unit to draw the correction pattern and corrects the landing position based on the reflected light detected by the light detection mechanism, wherein the head unit has a plurality of nozzle rows, the correction pattern is a pattern in which patches which are unit patterns corresponding to the amount of deviation of the landing position are arranged, and is a reference pattern which is drawn using only one of the nozzle rows which is a reference nozzle row in the head unit to determine the amount of deviation, and includes a reference pattern which includes a plurality of patches corresponding to different amounts of deviation, A printing system comprising: a target pattern which is a pattern including the patch drawn using a plurality of nozzle rows, including the target nozzle row which is the nozzle row to be corrected for impact position; wherein the control unit determines the amount of deviation of the impact position occurring between the reference nozzle row and the target nozzle row from the amount of reflected light from the positions of the plurality of patches in the reference pattern and the amount of reflected light from the positions of the patches in the target pattern, and corrects the impact position based on the determined amount of deviation.

2. The printing system according to claim 1, wherein the target pattern is a pattern including the patch drawn using the reference nozzle row and the target nozzle row, the amount of reflected light from the position of the patch in the target pattern changes according to the amount of displacement of the impact position that occurs between the reference nozzle row and the target nozzle row, and with respect to the amount of reflected light from the position of the patch in the target pattern, the maximum amount of light that occurs within a preset range of the amount of displacement of the impact position is defined as the maximum reflected light amount, and the minimum amount of light is defined as the minimum reflected light amount, the reference pattern includes a maximum reflected light amount corresponding patch which is the patch corresponding to the maximum reflected light amount, and a minimum reflected light amount corresponding patch which is the patch corresponding to the minimum reflected light amount.

3. The printing system according to claim 2, characterized in that the reference pattern further includes an intermediate reflected light amount corresponding patch, which is the patch corresponding to a light amount greater than the minimum reflected light amount and less than the maximum reflected light amount.

4. The printing system according to claim 1, wherein the target pattern is a pattern including the patch drawn using the reference nozzle row and the target nozzle row, the patch in the target pattern is a pattern of overlapping unit patterns, where a predetermined number of patterns with a width of 2N pixels (where N is an integer of 1 or more) in the main scanning direction are arranged with a gap of 2N pixels, the unit pattern drawn using the reference nozzle row and the unit pattern drawn using the target nozzle row overlap with their positions in the main scanning direction shifted by N pixels, the patch in the reference pattern is a pattern in which a first unit pattern drawn using the reference nozzle row and a second unit pattern drawn using the reference nozzle row overlap, the reference pattern includes a first patch in which the first unit pattern and the second unit pattern overlap with their positions aligned in the main scanning direction, and a second patch in which the first unit pattern and the second unit pattern overlap with their positions in the main scanning direction shifted by 2N pixels.

5. The printing system according to claim 1, characterized in that the head unit has a plurality of target nozzle rows, and there is one patch corresponding to one target nozzle row in the target pattern.

6. The printing system according to claim 1, wherein the patch in the target pattern has a reference nozzle row corresponding portion which is drawn using the reference nozzle row and a target nozzle row corresponding portion which is drawn using the target nozzle row, and the amount of reflected light changes according to the amount of the displacement of the impact position between the reference nozzle row and the target nozzle row.

7. An inkjet printing system comprising: a head unit having a nozzle row with a plurality of nozzles arranged in a line; a main scanning drive unit causing the head unit to perform a main scanning operation in which ink is ejected while moving in the main scanning direction relative to the medium to which the ink is to be ejected; a light detection mechanism for detecting reflected light from a correction pattern, which is a pattern used to correct the misalignment of the landing position of the ink ejected from the nozzles of the nozzle row; and a control unit that controls the operation of the head unit and the main scanning drive unit to cause the head unit to draw the correction pattern and correct the landing position based on the reflected light detected by the light detection mechanism, wherein the head unit has a first nozzle row, which is a first nozzle row, and a second nozzle row, which is a second nozzle row, and the correction pattern is a pattern in which patches, which are unit patterns corresponding to the amount of misalignment of the landing position, are arranged in a line, and the patch in which the amount of reflected light is maximum or minimum changes according to the amount of misalignment, and includes 2N+1 patches corresponding to the amount of misalignment of -N pixels (where N is an integer of 1 or more) or more and +N pixels or less. The control unit corrects the impact position based on the detected shift amount, which is the shift amount determined based on the reflected light, and defines a first pole state as a state in which the amount of reflected light is either maximum or minimum, and a second pole state as a state in which the other state occurs. When the amount of reflected light in any of the patches reaches the first pole state, the shift amount corresponding to the patch that reaches the first pole state is used as the detected shift amount. When the amount of reflected light in any of the patches does not reach the first pole state, and the amount of reflected light from the arranged patches increases or decreases monotonically, the shift amount corresponding to -N pixels or +N pixels is used as the detected shift amount, depending on how the amount of reflected light changes. When the amount of reflected light in any of the patches does not reach the first pole state, and the amount of reflected light from the patch position corresponding to the shift amount of +(N-1) pixels reaches the second pole state, the shift amount corresponding to -(N+1) pixels is used as the detected shift amount.A printing system characterized in that, in any of the aforementioned patches, the amount of reflected light does not reach the first polarity state, and the amount of reflected light from the patch position corresponding to the displacement amount of the -(N-1) pixel reaches the second polarity state, the displacement amount corresponding to the +(N+1) pixel is used as the detected displacement amount.

8. The printing system according to claim 1 or 7, further comprising a table on which the entire medium is placed on its upper surface, and a sub-scanning drive unit that moves the head unit in a sub-scanning direction perpendicular to the main scanning direction, wherein the control unit causes the head unit to print the correction pattern at a plurality of different positions on the medium placed on the table, and detects the amount of deviation at each of the plurality of positions on the table.

9. The printing system according to claim 8, characterized in that the control unit detects abnormal values ​​included in the detection results based on the detection results of the displacement amounts at multiple positions on the table.

10. A method for correcting the landing position of ink in a printing apparatus that performs printing using an inkjet method, comprising: a head unit having a nozzle row in which a plurality of nozzles are arranged; and a light detection mechanism that detects reflected light from a correction pattern, which is a pattern used to correct the deviation of the landing position of ink ejected from the nozzles of the nozzle row; the head unit is made to perform a main scanning operation in which it ejects ink while moving in the main scanning direction relative to the medium from which the ink is to be ejected; the head unit is made to draw the correction pattern; and the landing position is corrected based on the reflected light detected by the light detection mechanism; the head unit has a plurality of nozzle rows; the correction pattern is a pattern in which patches, which are unit patterns corresponding to the amount of deviation of the landing position, are arranged; the correction pattern is a reference pattern that is drawn using only one of the nozzle rows in the head unit, which is a reference nozzle row, to determine the amount of deviation; and includes a reference pattern which includes a plurality of patches corresponding to different amounts of deviation; A method for correcting the impact position, comprising: a target pattern which is a pattern including the patch drawn using a plurality of nozzle rows, including the target nozzle row which is the nozzle row to be corrected for impact position; and a method for correcting the impact position, characterized in that the amount of shift in the impact position occurring between the reference nozzle row and the target nozzle row is determined from the amount of reflected light from the positions of the plurality of patches in the reference pattern and the amount of reflected light from the positions of the patches in the target pattern, and the impact position is corrected based on the determined amount of shift.

11. A method for correcting the landing position of ink in a printing apparatus that performs printing using an inkjet method, comprising: a head unit having a nozzle row in which a plurality of nozzles are arranged; and a light detection mechanism that detects reflected light from a correction pattern, which is a pattern used to correct the misalignment of the landing position of ink ejected from the nozzles of the nozzle row; the head unit is made to perform a main scanning operation in which it ejects ink while moving in the main scanning direction relative to the medium from which the ink is to be ejected; the head unit is made to draw the correction pattern; and the landing position is corrected based on the reflected light detected by the light detection mechanism; the head unit has a first nozzle row, which is a first nozzle row; and a second nozzle row, which is a second nozzle row; the correction pattern is a pattern in which patches, which are unit patterns corresponding to the amount of misalignment of the landing position, are arranged, and the patch in which the amount of reflected light is maximum or minimum changes according to the amount of misalignment, and includes 2N+1 patches corresponding to the amount of misalignment of -N pixels (where N is an integer of 1 or more) or more and +N pixels or less; In the operation of correcting the impact position based on the detected shift amount, which is the shift amount identified based on the reflected light, when the state in which the amount of reflected light is either maximum or minimum is defined as the first pole state, and the state in which it is the other is defined as the second pole state, when the amount of reflected light in any of the patches is in the first pole state, the shift amount corresponding to the patch in the first pole state is used as the detected shift amount. When the amount of reflected light in any of the patches is not in the first pole state, and the amount of reflected light from the arranged patches is monotonically increasing or monotonically decreasing, the shift amount corresponding to -N pixels or +N pixels is used as the detected shift amount, depending on how the amount of reflected light changes. When the amount of reflected light in any of the patches is not in the first pole state, and the amount of reflected light from the patch corresponding to the shift amount of +(N-1) pixels is in the second pole state, the shift amount of -(N+1) pixels is used as the detected shift amount.A method for correcting the impact position, characterized in that, in any of the aforementioned patches, the amount of reflected light does not reach the first polarity state, and the amount of reflected light from the position of the patch corresponding to the displacement amount of the -(N-1) pixel reaches the second polarity state, the displacement amount of the +(N+1) pixel is used as the detected displacement amount.

12. A control device for correcting the ink landing position of a printing apparatus that performs printing using an inkjet method, the printing apparatus comprising: a head unit having a nozzle row in which a plurality of nozzles are arranged; a main scanning drive unit that causes the head unit to perform a main scanning operation in which ink is ejected while moving in the main scanning direction relative to the medium to which the ink is to be ejected; and a light detection mechanism that detects reflected light from a correction pattern which is a pattern used to correct the misalignment of the landing position of the ink ejected from the nozzles in the nozzle row, wherein the head unit has a plurality of the nozzle rows, and the correction pattern comprises: a pattern in which patches which are unit patterns corresponding to the amount of misalignment of the landing position are arranged, a reference pattern which is a pattern that serves as a reference for determining the amount of misalignment by being drawn using only one of the nozzle rows which is a reference nozzle row in the head unit, and includes a plurality of the patches which correspond to different amounts of misalignment; and a target pattern which is a pattern which includes the patches drawn using a plurality of nozzle rows which is the nozzle row to be corrected for the landing position, A control device characterized by controlling the operation of the head unit and the main scanning drive unit to cause the head unit to draw the correction pattern, correcting the impact position based on the reflected light detected by the light detection mechanism, determining the amount of deviation in the impact position between the reference nozzle row and the target nozzle row from the amount of reflected light from the positions of the multiple patches in the reference pattern and the amount of reflected light from the positions of the patches in the target pattern, and correcting the impact position based on the determined amount of deviation.

13. A control device for correcting the ink landing position of a printing apparatus that performs printing using an inkjet method, wherein the printing apparatus comprises a head unit having a nozzle row in which a plurality of nozzles are arranged, a main scanning drive unit that causes the head unit to perform a main scanning operation in which ink is ejected while moving in the main scanning direction relative to the medium to which the ink is to be ejected, and a light detection mechanism that detects reflected light from a correction pattern which is a pattern used to correct the misalignment of the landing position of the ink ejected from the nozzles of the nozzle row, wherein the head unit has a first nozzle row which is a first nozzle row, and a second nozzle row which is a second nozzle row, and the correction pattern is a pattern in which patches which are unit patterns corresponding to the amount of misalignment of the landing position are arranged, and the patch in which the amount of reflected light is maximum or minimum changes according to the amount of misalignment, and includes 2N+1 patches corresponding to the amount of misalignment of -N pixels (where N is an integer of 1 or more) or more and +N pixels or less. By controlling the operation of the head unit and the main scanning drive unit, the head unit is made to draw the correction pattern, and the impact position is corrected based on the detected shift amount, which is the shift amount identified based on the reflected light detected by the light detection mechanism. When the state in which the amount of reflected light is either maximum or minimum is defined as the first pole state, and the state in which it is the other is defined as the second pole state, when the amount of reflected light in any of the patches reaches the first pole state, the shift amount corresponding to the patch that reached the first pole state is used as the detected shift amount. When the amount of reflected light in any of the patches does not reach the first pole state, and the amount of reflected light from the arranged patches increases or decreases monotonically, the shift amount corresponding to -N pixels or +N pixels is used as the detected shift amount, depending on how the amount of reflected light changes. If the amount of reflected light in any of the aforementioned patches does not reach the first polarity state, and the amount of reflected light from the patch position corresponding to the displacement amount of the +(N-1) pixel reaches the second polarity state, then the displacement amount corresponding to the -(N+1) pixel is used as the detected displacement amount.A control device characterized in that, in any of the aforementioned patches, the amount of reflected light does not reach the first pole state, and the amount of reflected light from the patch position corresponding to the displacement amount of the -(N-1) pixel reaches the second pole state, the displacement amount corresponding to the +(N+1) pixel is used as the detected displacement amount.

Images