Printing apparatus and printing method

Abstract

A printing device and a printing method provide a proper test pattern for detecting a skew of a burst generated in image data as a reading result. The printing device has a conveyance section, a printing head having a plurality of nozzles that eject ink, and a control section that prints a test pattern for detecting a state of ink ejection from the nozzles to a printing medium, the test pattern having a first pattern element group in which pattern elements printed by the nozzles are arranged a plurality of times in a conveyance direction and a second pattern element group in which pattern elements printed by the nozzles are arranged a plurality of times in the conveyance direction. The control section prints the second pattern element group to the printing medium by causing the plurality of nozzles used for printing the first pattern element group to eject ink on the basis of the printing medium printed with the first pattern element group being conveyed by the conveyance section by a distance of a nozzle pitch or more.

Description

Technical Field

[0001] This invention relates to printing apparatus and printing method. Background Technology

[0002] A technology is disclosed as an inkjet printing device in which a recording head records a test pattern onto printing paper, a scanner reads the test pattern, the read data is interpolated, and the abnormality of the nozzle is determined based on the interpolated read data (see Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2007-54970

[0004] However, when a scanner reads a printed medium with a test pattern, sudden vibrations or external forces can sometimes cause skewing, such as stretching or contraction, in a portion of the read data. It is difficult to check whether the printing based on each nozzle is normal based on the skewed portion of the read data. Therefore, a test pattern that can easily detect such skew in the read data is needed. Summary of the Invention

[0005] A printing apparatus includes: a transport unit for transporting a printing medium in a transport direction; a print head having a plurality of nozzles for ejecting ink; and a control unit for controlling the transport unit and the print head to print a test pattern for detecting the state of ink ejection based on the nozzles onto the printing medium. The test pattern has: a first pattern element group, which is a plurality of pattern elements printed by the nozzles arranged in the transport direction; and a second pattern element group, which is a plurality of pattern elements printed by the nozzles arranged in the transport direction. The control unit prints the second pattern element group onto the printing medium by ejecting ink from the plurality of nozzles that printed the first pattern element group, based on a distance greater than or equal to the nozzle spacing in the transport direction, which is a distance by which the transport unit transports the printing medium that printed the first pattern element group by ejecting ink from the plurality of nozzles.

[0006] The printing method includes a printing step in which a printhead having a plurality of ink-ejecting nozzles prints a test pattern for checking the state of ink ejection based on the nozzles onto a printing medium. The test pattern has: a first pattern element group, which is a plurality of pattern elements printed by the nozzles arranged in the transport direction of the printing medium; and a second pattern element group, which is a plurality of pattern elements printed by the nozzles arranged in the transport direction. In the printing step, the second pattern element group is printed onto the printing medium by ejecting ink from the plurality of nozzles that printed the first pattern element group, based on a distance greater than or equal to the nozzle spacing in the transport direction, using the plurality of nozzles that printed the first pattern element group to eject ink. Attached Figure Description

[0007] Figure 1 This is a simplified block diagram illustrating the structure of the device.

[0008] Figure 2 This is a diagram showing a specific example of the configuration including the print head and the conveying section.

[0009] Figure 3 This diagram shows the relationship between the printing media and the printhead from an overhead perspective.

[0010] Figure 4 This is a flowchart illustrating the process from TP printing to nozzle inspection.

[0011] Figure 5 This diagram illustrates the process of printing TP onto the printing medium through steps S130 to S150.

[0012] Figure 6 This is a diagram showing printing media such as TP printed with various ink colors.

[0013] Figure 7 This is a diagram showing a portion of the image data being read.

[0014] Figure 8 This is a diagram illustrating the TP involved in other examples.

[0015] Label Explanation

[0016] 10… Printing apparatus; 11… Control unit; 11a… CPU; 11b… ROM; 11c… RAM; 12… Program; 12a… Printing control unit; 12b… Reading control unit; 12c… Inspection unit; 16… Transport unit; 17… Carriage; 18… Print head; 19… Reading unit; 21… Nozzle; 26, 26C, 26M, 26Y, 26K… Nozzle array; 30… Printing medium; 40C, 40M, 40Y, 40K… TP; 41C, 41M, 41Y, 41K… First pattern element group; 42C, 42M, 42Y, 42K… Second pattern element group; 51C, 52C… Pattern element; 51a, 52a… Pattern element image; 60… Read image data. Detailed Implementation

[0017] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, the drawings are merely examples for illustrating these embodiments. Since the drawings are examples, there may be inaccuracies in ratios or shapes, misalignment, or omissions.

[0018] 1. Device Composition:

[0019] Figure 1 The configuration of the printing apparatus 10 according to this embodiment is briefly shown.

[0020] The printing apparatus 10 includes a control unit 11, a display unit 13, an operation receiving unit 14, a communication interface 15, a transport unit 16, a carriage 17, a print head 18, and a reading unit 19. IF is short for interface. The control unit 11 is configured to include one or more ICs such as a CPU 11a, ROM 11b, and RAM 11c that serve as processors, as well as other non-volatile memories.

[0021] In the control unit 11, the processor, i.e., the CPU 11a, uses RAM 11c and the like as working areas to execute operations according to one or more programs 12 stored in ROM 11b, other memory, etc., thereby realizing various functions such as the printing control unit 12a, the read control unit 12b, and the inspection unit 12c. Furthermore, the processor is not limited to a single CPU; it can also be configured to process data using multiple CPUs, ASICs, or other hardware circuits, or it can be configured to process data by the CPU and hardware circuits working together.

[0022] Display unit 13 is a mechanism for displaying visual information, and may be composed of, for example, a liquid crystal display (LCD) or an organic EL display. Display unit 13 may also include a display and a driving circuit for driving the display. Operation receiving unit 14 is a mechanism for receiving user-based operations, such as through physical buttons, a touch panel, a mouse, or a keyboard. Obviously, a touch panel can also be implemented as a function of display unit 13.

[0023] The display unit 13 or the operation receiving unit 14 may be part of the printing apparatus 10, or it may be a peripheral device relative to the printing apparatus 10. The communication IF 15 is a general term for one or more IFs used by the printing apparatus 10 to connect to the outside via wired or wireless means in accordance with a predetermined communication protocol including known communication specifications.

[0024] The transport unit 16 is a mechanism for transporting the printing medium, including rollers and a motor that rotates the rollers. The print head 18 performs printing by ejecting ink from nozzles onto the printing medium via inkjet printing. The readout unit 19 is a mechanism for reading the printing result from the printing medium. The readout unit 19 is also referred to as a scanner. However, the printing apparatus 10 may also be configured without the readout unit 19.

[0025] The carriage 17 is a mechanism that receives power from a carriage motor (not shown) and is capable of reciprocating in a predetermined direction. The predetermined direction in which the carriage 17 is moved is also called the main scanning direction. The carriage 17 is as follows... Figure 2 or Figure 3 The image shows a printing head 18.

[0026] Figure 1 The printing apparatus 10 shown can be implemented by a single printer or by multiple devices that can be communicatively connected.

[0027] That is, the printing apparatus 10 can also be a printing system 10 in practice. The printing system 10 includes, for example, an information processing device that functions as a control unit 11 and a printer having a transport unit 16, a carriage 17, a print head 18, and even a reading unit 19. The printing method of this embodiment is realized by such a printing apparatus 10 or printing system 10.

[0028] In addition, the part of the control unit 11 that functions as the printing control unit 12a and the part that functions as the reading control unit 12b and the inspection unit 12c can also be separate information processing devices.

[0029] Figure 2 This illustrates a specific example of a portion of the printing apparatus 10, primarily comprising a print head 18 and a transport section 16. Figure 2 In the upper section, the above-mentioned specific example is shown from a perspective orthogonal to the transport direction D2 of the printing medium 30. Figure 2 The lower section shows a portion of the aforementioned specific example from an upward perspective.

[0030] The conveying unit 16 has an extraction shaft 22 upstream of the conveying direction and a winding shaft 25 downstream of the conveying direction. The upstream and downstream of the conveying direction are simply referred to as upstream and downstream. A long strip of printing medium 30, wound into a roller shape, is spread out along the conveying direction D2 via the extraction shaft 22 and the winding shaft 25. The printing medium 30 is conveyed in the conveying direction D2. The printing medium 30 can be paper or a medium made from materials other than paper.

[0031] exist Figure 2 In this example, the printing medium 30 wound on the extraction shaft 22 is extracted downstream by rotating the extraction shaft 22 clockwise. A front drive roller 23 is located downstream of the extraction shaft 22, and a rear drive roller 24 is located upstream of the winding shaft 25. The front drive roller 23, by rotating clockwise as described above, conveys the printing medium 30 extracted from the extraction section 22 downstream. A clamping roller 23n is provided for the front drive roller 23. The clamping roller 23n clamps the printing medium 30 between itself and the front drive roller 23 by abutting against the printing medium 30.

[0032] The printing medium 30, which is being conveyed downstream by the front drive roller 23, is further conveyed downstream by the rear drive roller 24 rotating clockwise as described above. A clamping roller 24n is provided for the rear drive roller 24. The clamping roller 24n clamps the printing medium 30 between itself and the rear drive roller 24 by abutting against the printing medium 30.

[0033] A print head 18 is disposed between the front drive roller 23 and the rear drive roller 24 to eject ink from the printing medium 30 from above. Figure 2 It is known that the printhead 18 is mounted on the carriage 17. The printhead 18 is capable of ejecting inks of various colors, such as cyan (C), magenta (M), yellow (Y), and black (K).

[0034] The printhead 18 has nozzles that open on the nozzle face 20 opposite to the printing medium 30. The printhead 18 ejects ink from the nozzles or not based on printing data. The ink ejected from the nozzles is also called ink droplets or ink dots. The printhead 18 can also be called a printing head, inkjet head, liquid ejection head, recording head, etc.

[0035] As the winding shaft 25 rotates clockwise as described above, the printed printing medium 30, conveyed by the rear drive roller 24, is wound onto the winding shaft 25.

[0036] A motor (not shown) used to properly rotate the extraction shaft 22, winding shaft 25, and various rollers is a specific example of the conveying unit 16 for conveying the printing medium 30. The number or arrangement of rollers arranged along the conveying path for conveying the printing medium 30 is not limited to... Figure 2The method shown is as described. Furthermore, the color of the ink ejected from the printhead 18 is not limited to the colors described above. Needless to say, a flat impression plate or the like can be provided between the front drive roller 23 and the rear drive roller 24 to support and receive the printing medium 30 ejected from the printhead 18 from below. Additionally, a portion of the printing medium 30 used for printing based on the printhead 18 can be cut off and recovered from an upstream portion of the printing medium 30 by a cutter (not shown) instead of being wound into a roller shape by the winding shaft 25.

[0037] exist Figure 2 In this example, the reading unit 19 is positioned downstream of the carriage 17 and the print head 18, and upstream of the rear drive roller 24. The reading unit 19 optically reads the printing medium 30 not printed by the print head 18 using an image sensor and outputs image data as the reading result. Figure 2 In the example, the reading unit 19 extends in the main scanning direction D1, which intersects the transport direction D2, and has a length that can cover the width of the printing medium 30, so that the printing medium 30 transported by the transport unit 16 is read in a stationary state.

[0038] Figure 3 The relationship between the printing medium 30 and the print head 18 is simply shown from a top view. The print head 18, mounted on the carriage 17, moves together with the carriage 17 from one end of the main scanning direction D1 to the other (outbound movement) and from the other end to one end (return movement). The main scanning direction D1 intersects the transport direction D2. This intersection can also be interpreted as orthogonal. Therefore, in Figure 2 In the upper section, the print head 18 is shown from a viewpoint parallel to the main scanning direction D1. However, due to various errors in the printer, such as those affecting the product, the main scanning direction D1 and the transport direction D2 may not be perfectly orthogonal. The transport direction is also referred to as the secondary scanning direction.

[0039] exist Figure 3 The image shows an example of the arrangement of nozzles 21 in the nozzle surface 20. Each small circle within the nozzle surface 20 is a nozzle 21. The printhead 18, in a configuration where ink of various colors is received from a liquid holding mechanism (not shown) such as an ink cartridge or ink reservoir, and ejected from the nozzles 21, has multiple nozzle rows 26. The nozzle row 26 consisting of nozzles 21 ejecting C ink is also referred to as nozzle row 26C. Similarly, sometimes the nozzle row 26 consisting of nozzles 21 ejecting M ink is referred to as nozzle row 26M, the nozzle row 26 consisting of nozzles 21 ejecting Y ink is referred to as nozzle row 26Y, and the nozzle row 26 consisting of nozzles 21 ejecting K ink is referred to as nozzle row 26K. Nozzle rows 26C, 26M, 26Y, and 26K are arranged along the main scanning direction D1.

[0040] Each nozzle array 26 is composed of multiple nozzles 21 whose spacing between them is fixed or approximately fixed, which is the distance between nozzles 21 in the conveying direction D2. The direction in which the multiple nozzles 21 constituting the nozzle array 26 are arranged is called the nozzle array direction D3. Figure 3 In the example, the nozzle array direction D3 is parallel to the transport direction D2. In a configuration where the nozzle array direction D3 is parallel to the transport direction D2, the nozzle array direction D3 is orthogonal to the main scanning direction D1. Alternatively, the nozzle array direction D3 may not be parallel to the transport direction D2, but may be configured to intersect the main scanning direction D1 at an angle.

[0041] The nozzle rows 26C, 26M, 26Y, and 26K on the transport direction D2 are each aligned with each other. The printing apparatus 10 performs a combination of transporting the printing medium 30 to the transport direction D2 and ink ejection based on the print head 18, which accompanies the movement of the carriage 17 along the main scanning direction D1, thereby printing an image onto the printing medium 30. The action of ink ejection from the print head 18 accompanying the outward and return movements of the carriage 17 is called "scanning" or "passing".

[0042] 2. Test pattern printing:

[0043] Figure 4 The flowchart illustrates the process executed by the control unit 11 according to procedure 12, from the printing of the test pattern (TP) to the inspection of the nozzle 21 based on the TP. TP is short for Test Pattern. The flowchart roughly consists of TP printing processing (step S100), obtaining the reading results of the printed TP (step S200), detecting sudden deviations based on the TP reading results (step S300), and inspecting the nozzle 21 based on the TP reading results (step S400). Step S100 corresponds to the TP printing process. Figure 4 In the text, step S100 is divided into steps S110 to S150, which are shown in detail.

[0044] In step S110, the printing control unit 12a acquires TP image data, which represents TP image data, from a storage source such as a predetermined memory or storage device that is communicative with the control unit 11. The TP image data is, for example, image data in bitmap form where the color of each pixel is defined by a predetermined color coordinate system. The color coordinate system referred to here includes, for example, various systems such as the RGB (red, green, blue) color coordinate system and the CMYK color coordinate system.

[0045] In step S120, the printing control unit 12a generates printing data for printing the TP based on the TP image data. The printing control unit 12a generates printing data that specifies whether ink is ejected (ink dot applied) or not ejected (ink dot not applied) per pixel and per ink color by performing predetermined image processing such as color conversion processing and midtone processing on the TP image data as needed. (See reference...) Figure 3 As explained above, assuming that the print head 18 uses four CMYK inks, in step S120, the print control unit 12a generates print data based on the TP image data, specifying the dot and undot areas per pixel and per CMYK.

[0046] The TP of this embodiment includes: a "first pattern element group" consisting of a plurality of "pattern elements" printed by nozzles 21 arranged in the transport direction D2; and a "second pattern element group" consisting of a plurality of such pattern elements arranged in the transport direction D2. One pattern element is printed by one nozzle 21. In addition, the first pattern element group and the second pattern element group are printed on the printing medium 30 with a positional relationship that is offset by a distance greater than or equal to the nozzle spacing in the transport direction D2.

[0047] Reference Figure 5 Specific instructions for steps S130 to S150.

[0048] Figure 5 This illustrates the process of printing TP onto the printing medium 30 through steps S130 to S150.

[0049] In step S130, the printing control unit 12a prints a first pattern element group onto the printing medium 30 based on printing data by controlling the movement of the carriage 17 along the main scanning direction D1 and the ink ejection based on the print head 18. Figure 5 On the left side, a portion of the nozzle array 26C and a portion of the printing medium 30 for printing the first pattern element group 41C are shown, and the state in which the first pattern element group 41C is printed onto the printing medium 30 in step S130 is also shown. Through the passage of the print head 18, C ink is ejected from each nozzle 21 of the nozzle array 26C, printing multiple pattern elements 51C. The first pattern element group 41C is composed of multiple pattern elements 51C arranged in the transport direction D2.

[0050] A pattern element 51C is a line parallel to the main scanning direction D1, formed by ink dots of C ink ejected from a nozzle 21 within a nozzle array 26C. Figure 5 In this text, the designation "P" indicates the nozzle spacing. That is, multiple pattern elements 51C are ideally arranged and printed in the transport direction D2 at intervals equal to the nozzle spacing P. Furthermore, in... Figure 5In order to distinguish the nozzles 21 within nozzle row 26C and to facilitate labeling each nozzle 21 with a nozzle number, specifically, each nozzle 21 is numbered sequentially from downstream to upstream as #1, #2, #3… Figure 5 In order to match the paper, five nozzles 21 numbered #1 to #5 are shown. Of course, the nozzle array 26C is composed of more nozzles 21, and each nozzle 21 of the nozzle array 26C prints pattern element 51C. The pattern element 51C that constitutes the first pattern element group 41C can also be called the "first pattern element".

[0051] After printing the first pattern element group in step S130, in step S140, the printing control unit 12a controls the transport unit 16 to transport the printing medium 30 with a predetermined offset. Here, the predetermined offset is set to twice the nozzle pitch P. That is, the printing medium 30 is transported downstream only at a distance of nozzle pitch P × 2. Figure 5 As can be seen, the result of such transport is that the position of the transport direction D2 of the pattern element 51C printed by nozzle 21 with nozzle number #3 in step S130 is consistent with or approximately consistent with nozzle 21 with nozzle number #1.

[0052] Following step S140, in step S150, the printing control unit 12a prints a second pattern element group onto the printing medium 30 based on printing data by controlling the movement of the carriage 17 along the main scanning direction D1 and the ink ejection based on the print head 18. Figure 5 On the right side, a portion of the nozzle array 26C and a portion of the printing medium 30 for printing the second pattern element group 42C are shown, and the state in which the second pattern element group 42C is printed onto the printing medium 30 after step S150 is also shown. That is, after printing the first pattern element group 41C through the nozzle array 26C, the second pattern element group 42C is printed through the same nozzle array 26C after a predetermined staggered transport. Through the passage of the print head 18, C ink is ejected from each nozzle 21 of the nozzle array 26C, and a plurality of pattern elements 52C are printed. The second pattern element group 42C is composed of a plurality of pattern elements 52C arranged in the transport direction D2.

[0053] Pattern element 52C is the same as pattern element 51C, and is a line formed by ink dots of C ink ejected from one nozzle 21 within the nozzle array 26C, parallel to the main scanning direction D1. Pattern elements 51C are in the same relationship to each other, and multiple pattern elements 52C are ideally arranged and printed in the transport direction D2 at the same interval as the nozzle spacing P. The pattern elements 52C constituting the second pattern element group 42C can also be referred to as "second pattern elements".

[0054] The result of printing the second pattern element group 42C in step S150 is that, from Figure 5 It can be seen that the position of the conveying direction D2 of the pattern element 52C printed by nozzle 21 with nozzle number #1 is the same as or approximately the same as the pattern element 51C printed by nozzle 21 with nozzle number #3 in step S130.

[0055] In summary, the TP having the first pattern element group and the second pattern element group is printed onto the printing medium 30. Of course, nozzle rows 26M, 26Y, and 26K other than nozzle row 26C also print the first pattern element group in step S130 and the second pattern element group in step S150, respectively.

[0056] Figure 6 The result of step S100 is that printing media 30 is printed with TP40C, 40M, 40Y, and 40K inks of individual colors. TP40C, if used... Figure 5 The first pattern element group 41C and the second pattern element group 42C are constructed by printing C ink through each nozzle 21 of nozzle array 26C. Similarly, TP40M is constructed by printing the first pattern element group 41M and the second pattern element group 42M by printing M ink through each nozzle 21 of nozzle array 26M. TP40Y is constructed by printing the first pattern element group 41Y and the second pattern element group 42Y by printing Y ink through each nozzle 21 of nozzle array 26Y. TP40K is constructed by printing the first pattern element group 41K and the second pattern element group 42K by printing K ink through each nozzle 21 of nozzle array 26K.

[0057] That is, in step S130, the first pattern element group 41C, the first pattern element group 41M, the first pattern element group 41Y, and the first pattern element group 41K are printed through the passage of the print head 18. And, after the transport in step S140, in step S150, the second pattern element group 42C, the second pattern element group 42M, the second pattern element group 42Y, and the second pattern element group 42K are printed through the passage of the print head 18.

[0058] from Figure 5 or Figure 6 It can be seen that the first pattern element group and the second pattern element group constituting a TP, i.e., a TP of an ink color, are arranged in adjacent positions on the main scanning direction D1. For example, on the main scanning direction D1, no TP based on other inks is printed between the first pattern element group 41C and the second pattern element group 42C based on ink C.

[0059] 3. Post-printing processing of test patterns:

[0060] In step S200, the reading control unit 12b controls the reading unit 19 to perform reading of the printed medium 30 after printing TP in step S100, and obtains image data, i.e., read image data, as the reading result from the reading unit 19. Obviously, the transport unit 16 performs the transport of the amount of printed medium 30 required for the reading unit 19 to read the printed medium 30.

[0061] Figure 6 The reading unit 19 is shown, located downstream of the printing medium 30. As the printing medium 30, conveyed downstream by the transport unit 16, passes below the reading unit 19, the printing medium 30 is read by the reading unit 19. Figure 6 In this example, the reading unit 19 is configured by connecting multiple sensor chips 191, 192, 193, and 194 in the main scanning direction D1. Each of the multiple sensor chips 191, 192, 193, and 194 has an image sensor and reads a predetermined range of the transported printing medium 30.

[0062] In step S200, the control unit 11 only needs to obtain the reading result of the printing medium 30 printed with TP. Therefore, the user can also use an external scanner to read the printing medium 30 printed with TP, and the printing apparatus 10 can obtain the read image data from the scanner via communication IF15.

[0063] In step S300, the inspection unit 12c performs a "sudden deviation" detection based on the read image data acquired in step S200. A sudden deviation refers to a distortion, such as stretching or contraction, that occurs in a portion of the read image data when the read unit 19 or scanner reads the printed medium 30 printed with TP, caused by sudden vibrations or external forces on the printed medium 30 or the read unit 19. Sudden vibrations or external forces can occur due to, for example, during the reading of the printed medium 30, the user touching the printing apparatus 10 or scanner, the user walking in the vicinity, or the shape of the transport path of the printed medium 30. In the subsequent inspection step S400, step S300 is performed to prevent the sudden deviation from being confused with positional deviations of pattern elements due to abnormalities in the nozzle 21.

[0064] Figure 7 This shows a portion of the image data 60 acquired in step S200. Figure 7 The image shows a portion of the reading results for a certain ink color's TP. Specifically, reference numerals 51a and 52a are images representing the reading results of pattern elements printed on the printing medium 30, and these are referred to as pattern element images 51a and 52a. For example, multiple pattern element images 51a constitute... Figure 5 The image shown is a reading result of multiple pattern elements 51C of the first pattern element group 41C. The image 52a is a reading result of multiple pattern elements 52C constituting the second pattern element group 42C.

[0065] The inspection unit 12c detects sudden deviations by evaluating the differences between multiple pattern element images 51a, which are images of the first pattern element group, and multiple pattern element images 52a, which are images of the second pattern element group, in the read image data 60.

[0066] The following are specific examples of methods for detecting sudden deviations.

[0067] Inspection unit 12c calculates the deviation ΔP(n) and deviation ΔP(nN) as follows.

[0068] ΔP(n)=P(n)-P(n)'

[0069] ΔP(nN)=P(nN)-P(nN)'

[0070] The deviation ΔP(n) or deviation ΔP(nN) corresponds to the difference between pattern element image 51a and pattern element image 52a.

[0071] In each formula, n is an integer greater than or equal to 1. P(n) is the nth "pattern element spacing" counting from the downstream side in the reading result of the first pattern element group. The pattern element spacing in the reading result of the first pattern element group refers to the interval of the pattern element images 51a in the transport direction D2. Figure 7 In the diagram, pattern element images 51a and 52a are marked with parentheses and nozzle numbers. This indicates which nozzle 21 printed the read pattern element for each of the pattern element images 51a and 52a. In this embodiment, for the first pattern element group, the interval between the pattern element image 51a of the pattern element printed by the nozzle 21 with nozzle number #n and the pattern element image 51a of the pattern element printed by the nozzle 21 with nozzle number #n+1 is set to P(n). Therefore, for example, the interval between the pattern element image 51a of the pattern element 51C printed by the nozzle 21 with nozzle number #3 and the pattern element image 51a of the pattern element 51C printed by the nozzle 21 with nozzle number #4 is the pattern element spacing P3. Figure 7 The example shows the spacing between pattern elements P1, P2, P3, and P4.

[0072] P(n)' is the nth pattern element spacing from the downstream side in the reading result of the second pattern element group. The pattern element spacing in the reading result of the second pattern element group is the interval of the pattern element images 52a in the transport direction D2. In this embodiment, for the second pattern element group, the interval between the pattern element image 52a of the pattern element printed by the nozzle 21 with nozzle number #n and the pattern element image 52a of the pattern element printed by the nozzle 21 with nozzle number #n+1 is set as P(n)'. For example, the interval between the pattern element image 52a of the pattern element 52C printed by the nozzle 21 with nozzle number #3 and the pattern element image 52a of the pattern element 52C printed by the nozzle 21 with nozzle number #4 is the pattern element spacing P3'. Figure 7 The example shows the spacing between pattern elements P1', P2', P3', and P4'.

[0073] The deviation ΔP(n) is the difference between the pattern element spacing P(n) and the pattern element spacing P(n)'.

[0074] Similarly, P(nN) is the spacing of the nNth pattern element counting from the downstream side in the reading result of the first pattern element group. Additionally, P(nN)' is the spacing of the nNth pattern element counting from the downstream side in the reading result of the second pattern element group.

[0075] N is a value corresponding to the predetermined offset amount used in step S140. The unit of the predetermined offset amount is the nozzle spacing P, and as mentioned above, the predetermined offset amount is nozzle spacing P × 2, so N = 2 here.

[0076] Therefore, the pattern element spacing P(n) and the pattern element spacing P(nN)', such as the pattern element spacing P3 and the pattern element spacing P1', have a common positional relationship in the transport direction D2 within the image data 60 being read.

[0077] The deviation ΔP(nN) is the difference between the pattern element spacing P(nN) and the pattern element spacing P(nN)'.

[0078] Pattern element spacing P(n) and pattern element spacing P(n)' refer to the distance between pattern elements printed by two nozzles 21 with the same combination. Therefore, ideally, without sudden deviations, the deviation ΔP(n) is 0. Similarly, pattern element spacing P(nN) and pattern element spacing P(nN)' refer to the distance between pattern elements printed by two nozzles 21 with the same combination. Therefore, ideally, the deviation ΔP(nN) is 0.

[0079] In addition, the pattern element spacing P(n) and the pattern element spacing P(nN') are in a common positional relationship in the transport direction D2, and therefore are in a relationship that includes the same sudden deviation.

[0080] Therefore, when all of the following conditions 1 to 3 are met, the inspection unit 12c determines that the pattern element spacing P(n) and the pattern element spacing P(nN)' have sudden deviations.

[0081] Condition 1: The sign of ΔP(n) is opposite to the sign of ΔP(nN).

[0082] Condition 2: The absolute value of ΔP(n) + ΔP(nN) is less than the predetermined first threshold.

[0083] Condition 3: The absolute values ​​of ΔP(n) and ΔP(nN) are both greater than a predetermined second threshold. Furthermore, the first threshold is assumed to be less than the second threshold.

[0084] For example, when focusing on the case where n=3, the sign of ΔP3=P3-P3' is positive, and the sign of ΔP1=P1-P1' is negative, thus satisfying condition 1. Furthermore, if the absolute value of (P3-P3')+(P1-P1') is less than the first threshold, and the absolute values ​​of (P3-P3') and (P1-P1') are greater than the second thresholds respectively, then conditions 2 and 3 are also satisfied. When n=3, and conditions 1 to 3 are met, the inspection unit 12c determines that there is a sudden deviation in the pattern element spacing P3 and the pattern element spacing P1'.

[0085] Reference Figure 5 , 7 At the same time, after simultaneously reading the pattern element 51C printed by nozzle 21 with nozzle number #3 and the pattern element 52C printed by nozzle 21 with nozzle number #1, it takes a necessary amount of time to read the pattern element 51C printed by nozzle 21 with nozzle number #4 and the pattern element 52C printed by nozzle 21 with nozzle number #2. During this time, the pattern element spacing P3 and pattern element spacing P1', which are part of the image data 60 being read, extend in the transport direction D2. This extension is a type of sudden deviation.

[0086] In step S400, the inspection unit 12c checks the ink ejection status of the nozzles 21 of the printhead 18 based on the read image data acquired in step S200 and the detection results of sudden deviations in step S300. The ink ejection status is categorized as normal or abnormal. An abnormality refers to a deviation in the ink dot's ejection position from the ideal position, such as an ejection position deviation. The inspection unit 12c compares the spacing between each pattern element in the read image data with a predetermined reference value for the pattern element spacing. For nozzles 21 involved in printing with pattern element spacing that is, for example, narrower or wider than the reference value, it is determined to be abnormal. Specifically, the inspection unit 12c excludes pattern element spacing that is determined to have sudden deviations in step S300 from the inspection in step S400.

[0087] For example, if the detection of sudden deviations in pattern element spacing P3 and pattern element spacing P1' as described above is successful, the inspection unit 12c will not consider pattern element spacing P3 and pattern element spacing P1', and their upstream adjacent pattern element spacings P4 and P2', as inspection objects in step S400. The inspection unit 12c in... Figure 7 In the example, the pattern element spacings P1, P2, P3', and P4' in the read image data 60 are set as objects, and the inspection in step S400 is performed. Therefore, by checking whether the nozzle 21 is normal or abnormal based on pattern element spacings that are highly likely to become inappropriate due to sudden deviations, it is possible to avoid misjudging a portion of the nozzles 21 as abnormal. The inspection unit 12c stores the inspection results based on step S400. End of section. Figure 4 The flowchart.

[0088] 4. Summary and explanation of results:

[0089] Therefore, according to this embodiment, the printing apparatus 10 includes: a transport section 16 for transporting a printing medium 30 in a transport direction D2; a print head 18 having a plurality of ink-ejecting nozzles 21; and a control section 11 for printing a TP (printer unit) for checking the state of ink ejection based on the nozzles 21 onto the printing medium 30 by controlling the transport section 16 and the print head 18. The TP has: a first pattern element group 41C formed by arranging a plurality of pattern elements 51C printed by the nozzles 21 in the transport direction D2; and a second pattern element group 42C formed by arranging a plurality of pattern elements 52C printed by the nozzles 21 in the transport direction D2. Furthermore, the control section 11, based on a predetermined offset amount in the transport direction D2 of the printing medium 30 on which the first pattern element group 41C has been printed by ejecting ink from the plurality of nozzles 21, prints the second pattern element group 42C onto the printing medium 30 by ejecting ink from the plurality of nozzles 21 that printed the first pattern element group 41C.

[0090] The predetermined offset is set to a distance of at least the nozzle spacing P. With this configuration, the printing apparatus 10 can print TP suitable for detecting sudden deviations. That is, in this embodiment, using a common plurality of nozzles, a first pattern element group and a second pattern element group, which are substantially identical images, are printed with a nozzle spacing P or more offset in the transport direction D2. Therefore, by comparing the pattern element spacing corresponding to the first pattern element group and the pattern element spacing corresponding to the second pattern element group in the read image data of the TP, it is possible to appropriately detect which part of the read image data has a sudden deviation due to a reading defect. Furthermore, by appropriately detecting sudden deviations, the accuracy of the inspection of whether the nozzle 21 is normal or abnormal based on the read image data of the TP can be improved.

[0091] As described above, by setting the predetermined offset amount to a distance greater than or equal to the nozzle spacing P, a sudden deviation occurs between the spacing of a pattern element in the first pattern element group and the spacing of a pattern element in the second pattern element group, which should have the same spacing, within the read image data. That is, the presence or absence of a sudden deviation can be determined by evaluating the deviation amount ΔP(n) or the deviation amount ΔP(nN).

[0092] As a preferred example, the control unit 11 may also print the second pattern element group onto the printing medium 30 by conveying the printing medium 30, on which the first pattern element group has been printed, a distance more than twice the nozzle spacing P by the conveying unit 16. That is, as Figure 5 As shown, the predetermined offset amount can also be the nozzle spacing P×2.

[0093] If the predetermined offset is set to a distance more than twice the nozzle spacing P, then even if the spacing of pattern elements where a sudden deviation is detected and the spacing of pattern elements adjacent to that pattern element spacing upstream are not the objects of inspection in step S400, the inspection of each nozzle 21 can be appropriately performed based on the read image data. That is, according to Figure 7 For example, even if the pattern element spacing P3 and P4 are not the objects to be checked in step S400, the nozzles 21 with nozzle numbers #3 and #4 can be checked by referring to the pattern element spacing P3' and P4' instead of these.

[0094] When the printing medium 30 printed with TP is conveyed by the transport unit 16, it is sometimes conveyed in an inclined position relative to the transport direction D2. When the printing medium 30 is inclined, the greater the distance between the first pattern element group and the second pattern element group in the main scanning direction D1, the greater the positional relationship between them in the transport direction D2 exceeds the predetermined misalignment amount, causing a deviation. This makes it difficult to detect sudden deviations using the aforementioned sudden deviation detection method. Therefore, in this embodiment, as... Figure 6As shown, the first and second pattern element groups constituting the TP can also be arranged in adjacent positions on the main scanning direction D1. With this configuration, when reading from a printing medium 30 printed with the TP in an inclined state, the positional relationship between the read images of the first and second pattern element groups on the transport direction D2 remains approximately normal, and sudden deviations can be detected.

[0095] According to this embodiment, the printing apparatus 10 may also have a reading unit 19 for reading the printing medium 30 printed with TP, located further downstream of the print head 18 in the transport direction D2. Additionally, Figure 6 In this example, the reading unit 19 has multiple sensor chips, which have image sensors for reading.

[0096] Furthermore, the first and second pattern element groups constituting the TP can also be configured at positions that can be read by a common sensor chip.

[0097] exist Figure 6 In the example, at the location read by the sensor chip 191 in the printing medium 30, TP40C based on the first pattern element group 41C and the second pattern element group 42C is printed. Additionally, in Figure 6 In the example, TP40M is printed at the position read by sensor chip 192 in the printing medium 30, TP40Y is printed at the position read by sensor chip 193, and TP40K is printed at the position read by sensor chip 194. Because each sensor chip has inherent output characteristics or deviations in their relative positions, there may sometimes be deviations in color or position in the readings output by each sensor chip. For example... Figure 6 As in the example, the first pattern element group and the second pattern element group constituting the TP are in a positional relationship that is read by a common sensor chip, so that the reading values ​​of the first pattern element group and the second pattern element group do not produce various deviations caused by the different sensor chips, thereby improving the detection accuracy of sudden deviations based on the reading values ​​of the first pattern element group and the second pattern element group.

[0098] This embodiment also discloses various types of inventions, such as methods and procedures 12, other than printing apparatus 10 and printing system 10.

[0099] The printing method includes a printing step in which a print head 18 having a plurality of ink-ejecting nozzles 21 is used to print a TP (printed with ink) for checking the state of ink ejection based on the nozzles 21 onto a printing medium 30. The TP has: a first pattern element group consisting of a plurality of pattern elements printed by the nozzles 21 arranged in the transport direction D2 of the printing medium 30; and a second pattern element group consisting of a plurality of pattern elements printed by the nozzles 21 arranged in the transport direction D2. In the printing step, the second pattern element group is printed onto the printing medium 30 by ejecting ink from the plurality of nozzles 21 to print the first pattern element group, based on a distance of at least a nozzle pitch P, which is the interval between the nozzles 21 in the transport direction D2, while the printing medium 30 is transported by the plurality of nozzles 21 that printed the first pattern element group.

[0100] 5. Other implementation methods:

[0101] Other methods included in this implementation are described.

[0102] The pattern elements constituting the first pattern element group of the TP do not need to be in the same position in the main scanning direction D1. Similarly, the pattern elements constituting the second pattern element group of the TP do not need to be in the same position in the main scanning direction D1. Alternatively, the pattern elements constituting the first pattern element group can be staggered in the main scanning direction D1 with their positions in the main scanning direction D1 being consistent for a predetermined number of periods, and similarly, the pattern elements constituting the second pattern element group can be staggered in the main scanning direction D1 with their positions in the main scanning direction D1 being consistent for the aforementioned predetermined number of periods.

[0103] Figure 8 An example of a portion of TP printed on printing medium 30. Figure 8 and Figure 5 Similarly, the right-hand diagram shows the state at the end of printing of the second pattern element group based on step S150. As explained so far, the first pattern element group 41C is composed of a plurality of pattern elements 51C with intervals corresponding to the nozzle spacing P in the transport direction D2, and the second pattern element group 42C, which is offset from the first pattern element group 41C by a predetermined offset amount in the transport direction D2, is composed of a plurality of pattern elements 52C with intervals corresponding to the nozzle spacing P in the transport direction D2. Furthermore, according to Figure 8 Each pattern element 51C is arranged in a staggered manner along the main scanning direction D1, with its position consistent across three cycles. Similarly, each pattern element 52C is also arranged in a staggered manner along the main scanning direction D1, with its position consistent across three cycles. That is, Figure 8The case where the predetermined number is 3 is shown. The predetermined number can also be 2 or more. By printing the pattern elements staggered in the main scanning direction D1, the inspection unit 12c can easily determine each pattern element individually when detecting sudden deviations in the image data and inspecting the nozzle 21. In addition, the user can also easily visually confirm each pattern element individually.

[0104] Obviously, the printing medium 30 may not be wound up. Figure 2 Continuous paper in a roller shape, as shown in the example. Printing medium 30 can also be single sheets of paper cut into page units, etc.

[0105] If the detection of a sudden deviation in step S300 is successful, the control unit 11 may skip the check in step S400 and rescan the printed TP from step S100. For example, if the detection of a sudden deviation in step S300 is successful, the control unit 11 returns the printing medium 30 by the transport unit 16. Returning refers to the process of transporting the printing medium 30 from downstream to upstream. If the control unit 11 returns the TP-printed portion of the returned printing medium 30 to a position upstream of the reading unit 19, it restarts the transport of the downstream printing medium 30, causing the reading unit 19 to read the TP-printed portion of the printing medium 30. Thus, the control unit 11 reacquires the read image data (step S200) and can perform step S300 based on this read image data.

[0106] The TP may also have a third pattern element group, which is composed of multiple pattern elements printed by the nozzles 21 arranged in the transport direction D2, and offset by a predetermined offset amount relative to the first pattern element group in the opposite direction to the second pattern element group. That is, in step S100, the printing control unit 12a prints the TP onto the printing medium 30 by processing in the following order: printing the third pattern element group based on the passage of the print head 18, transporting the printing medium 30 with a predetermined offset amount, printing the first pattern element group, transporting the printing medium 30 with a predetermined offset amount, and printing the second pattern element group. The third pattern element group is also an image that is substantially the same as the first or second pattern element group. In this case, when the predetermined offset amount is set to the nozzle spacing P×2, the pattern elements printed by the nozzle 21 with nozzle number #5 in the third pattern element group, the pattern elements printed by the nozzle 21 with nozzle number #3 in the first pattern element group, and the pattern elements printed by the nozzle 21 with nozzle number #1 in the second pattern element group are aligned in the transport direction D2 in the printing medium 30. In addition, the third pattern element group, the first pattern element group, and the second pattern element group are arranged in this order on the main scanning direction D1.

[0107] Based on this configuration, in the image data read by TP, the pattern element spacing between pattern element images 51a corresponding to the first pattern element group is consistent in position along the transport direction D2 with respect to either the pattern element spacing between pattern element images 52a corresponding to the second pattern element group or the pattern element spacing between pattern element images corresponding to the third pattern element group. Therefore, in step S300, the inspection unit 12c can set all pattern element spacings P1, P2, P3, and P4 between pattern element images 51a corresponding to the first pattern element group as objects for detecting sudden deviations.

[0108] The reading unit 19 does not need to be positioned further downstream than the printing medium 30, but it can also be positioned further upstream than the printing medium 30.

[0109] The reading unit 19 does not need to be a fixed linear scan; it can also be a moving serial scan, for example, in which the reading unit 19 reads while moving in the main scan direction D1.

[0110] A pattern element 51C does not need to be a line; it can also be, for example, a dot.

[0111] It is not necessary to print the second pattern element group for all ink colors, or it is possible to print the second pattern element group only for one ink color.

Claims

1. A printing apparatus, characterized in that, have: The conveying unit transports the printing media in the conveying direction; A printhead with multiple ink ejection nozzles; and The control unit, by controlling the transport unit and the print head, prints a test pattern for detecting the state of ink ejection based on the nozzle onto the printing medium. The test pattern comprises: a first pattern element group, consisting of multiple pattern elements printed by the nozzle arranged in the conveying direction; and a second pattern element group, consisting of multiple pattern elements printed by the nozzle arranged in the conveying direction. The control unit, based on the distance of the printing medium for printing the first pattern element group by ejecting ink from the plurality of nozzles by the transport unit (a distance greater than or equal to the nozzle spacing in the transport direction), moves the print head along a main scanning direction that intersects the transport direction, and then prints the second pattern element group onto the printing medium by ejecting ink from the plurality of nozzles used for printing the first pattern element group.

2. The printing apparatus according to claim 1, characterized in that, The control unit prints the second pattern element group onto the printing medium by conveying the printing medium for printing the first pattern element group a distance greater than twice the nozzle spacing by the conveying unit.

3. The printing apparatus according to claim 1 or 2, characterized in that, The pattern elements constituting the first pattern element group are staggered in the main scanning direction in such a way that their positions are consistent in a predetermined number of periods in the main scanning direction. The pattern elements constituting the second pattern element group are staggered in the main scanning direction in such a way that their positions in the main scanning direction are consistent with the predetermined number of periods.

4. The printing apparatus according to claim 1 or 2, characterized in that, The first pattern element group and the second pattern element group are positioned adjacent to each other in the main scanning direction that intersects the transport direction.

5. The printing apparatus according to claim 1 or 2, characterized in that, A reading section is located downstream of the print head in the conveying direction to read the printing medium on which the test pattern is printed. The reading unit has multiple sensor chips, and each sensor chip has an image sensor for reading. The first pattern element group and the second pattern element group are configured at positions that can be read by the common sensor chip.

6. A printing method, characterized in that, The process includes a printing step in which a printhead with multiple ink-ejecting nozzles is used to print a test pattern onto a printing medium for checking the state of ink ejection based on the nozzles. The test pattern comprises: a first pattern element group, consisting of multiple pattern elements printed by the nozzle arranged in the transport direction of the printing medium; and a second pattern element group, consisting of multiple pattern elements printed by the nozzle arranged in the transport direction. In the printing process, the print head is moved along a main scanning direction that intersects the transport direction by conveying the printing medium for printing the first pattern element group by ejecting ink from the plurality of nozzles. Then, the second pattern element group is printed onto the printing medium by ejecting ink from the plurality of nozzles used for printing the first pattern element group.

Images