Attitude calibration method of printing head, electronic equipment, printing system and medium

Abstract

The invention discloses an attitude calibration method of a printing head, electronic equipment, a printing system and a medium, and relates to the technical field of printing head calibration, and the attitude calibration method of the printing head comprises the following steps: controlling the printing head to print a target calibration pattern corresponding to a target calibration axis; obtaining a target calibration image containing the target calibration pattern; and calculating a target calibration angle of the target calibration axis based on the target calibration image so as to adjust the attitude of the target calibration axis based on the target calibration angle. The target calibration angle is accurately determined based on the calibration image, and the number of times of repeated adjustment due to inaccurate adjustment is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of print head calibration, and in particular to a print head posture calibration method, electronic equipment, printing system and medium. Background Art

[0002] In printing equipment, the position accuracy of the print head directly affects the image quality. After the first installation or long-term use, the print head may produce micron-level deviations in the three axes of X / Y / Z due to mechanical vibration, component wear or material thermal deformation, resulting in defects such as stripes, ghosting or local distortion in the printed image. Therefore, an automatic calibration solution for the print head is urgently needed. Summary of the invention

[0003] The main purpose of the present application is to provide a print head posture calibration method, electronic device, printing system and medium, aiming to solve the technical problem of low adjustment accuracy due to the need for manual determination of the adjustment angle and manual adjustment.

[0004] To achieve the above object, the present application provides a method for calibrating the posture of a print head, the method comprising:

[0005] Controlling the print head to print a target calibration pattern corresponding to the target calibration axis;

[0006] Acquire a target calibration image including the target calibration pattern;

[0007] A target calibration angle of the target calibration axis is calculated based on the target calibration image to adjust the posture of the target calibration axis based on the target calibration angle.

[0008] In one embodiment, if the target calibration axis is a z-axis, the step of controlling the print head to print a target calibration pattern corresponding to the target calibration axis includes:

[0009] Controlling all nozzles corresponding to each color in the print head to discharge ink to print a first target calibration sub-pattern;

[0010] Controlling the paper feeding mechanism to move the printing medium by a first preset distance;

[0011] All the nozzles corresponding to each color are controlled to discharge ink to print a second target calibration sub-pattern, and the target calibration pattern corresponding to the z-axis includes the first target calibration sub-pattern and the second target calibration sub-pattern.

[0012] In one embodiment, the first target calibration sub-pattern includes first lines of each color, the second target calibration sub-pattern includes second lines of each color, and the step of calculating the target calibration angle of the target calibration axis based on the target calibration image includes:

[0013] identifying the first line and the second line in the target calibration image;

[0014] Extracting first feature points on the first line and second feature points on the second line of the same color;

[0015] A target calibration angle of the z-axis is calculated according to the physical coordinates of the first feature point and the second feature point.

[0016] In one embodiment, if the target calibration axis is the y-axis, the step of controlling the print head to print the target calibration pattern corresponding to the target calibration axis includes:

[0017] All the nozzles corresponding to each color are controlled to discharge ink to print the target calibration pattern corresponding to the Y axis.

[0018] In one embodiment, if the target calibration axis is an x-axis, the step of controlling the print head to print a target calibration pattern corresponding to the target calibration axis includes:

[0019] Determine the target nozzle corresponding to each color according to the preset number;

[0020] The target nozzles of each color are controlled to discharge ink according to the arrangement order of each color, and the print head is controlled to move a second preset distance along the x-axis while the target nozzles of each color discharge ink, so as to print the target calibration pattern corresponding to the x-axis.

[0021] In one embodiment, after controlling the target nozzle corresponding to the current color to discharge ink, and before controlling the target nozzle corresponding to the next color to discharge ink, the print head posture calibration method further includes:

[0022] The print head is controlled not to output ink, and at the same time, the print head is controlled to move a third preset distance along the x-axis.

[0023] In one embodiment, the target calibration pattern includes target lines, and the step of calculating the target calibration angle of the target calibration axis based on the target calibration image includes:

[0024] Determining at least three target lines and at least two target line pairs in the target calibration image, wherein the target line pairs include two target lines;

[0025] Obtaining a first distance and a second distance according to a distance between two target lines in the at least two target line pairs;

[0026] Determining a tilt direction on the target calibration axis according to a magnitude relationship between the first distance and the second distance;

[0027] Determine a tilt angle value according to the first distance, the second distance and a reference distance;

[0028] The target calibration angle is determined based on the tilt direction and the tilt angle value.

[0029] In one embodiment, along the positive direction of the target calibration axis, the first distance is in the negative direction of the second distance, and the step of determining the tilt direction on the target calibration axis according to the magnitude relationship between the first distance and the second distance includes:

[0030] If the first distance is greater than the second distance, the tilt direction is negative;

[0031] If the first distance is smaller than the second distance, the tilt direction is positive.

[0032] In one embodiment, the step of determining the tilt angle value according to the first distance, the second distance and a reference distance comprises:

[0033] Calculating a first ratio of the first distance to the reference distance, and a second ratio of the second distance to the reference distance;

[0034] determining a first angle according to the first ratio, and determining a second angle according to the second ratio;

[0035] If the first angle is smaller than the second angle, the first angle is used as the tilt angle value;

[0036] If the first angle is greater than the second angle, the second angle is used as the tilt angle value.

[0037] In one embodiment, before the step of controlling the print head to print the target calibration pattern corresponding to the target calibration axis, the step includes:

[0038] Get the calibration order of each calibration axis;

[0039] determining the target calibration axis according to the calibration sequence;

[0040] According to the calibration sequence, each target calibration axis is calibrated in turn to obtain a target calibration angle corresponding to each target calibration axis.

[0041] In one embodiment, after the step of calculating the target calibration angle of the target calibration axis based on the target calibration image, the method further comprises:

[0042] If the absolute value of the target calibration angle is greater than a preset threshold, the posture of the target calibration axis is adjusted based on the target calibration angle.

[0043] In addition, to achieve the above-mentioned purpose, the present application also provides an electronic device, which includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program is configured to implement the steps of the print head posture calibration method as described above.

[0044] In addition, to achieve the above-mentioned purpose, the present application also provides a printing system, the printing system comprising a host computer and an inkjet printing device, the host computer being communicatively connected to the inkjet printing device;

[0045] The host computer is used to obtain the target calibration angle of the target calibration axis based on the steps of the print head posture calibration method as described above, and send the target calibration angle to the inkjet printing device; the inkjet printing device is used to control the print head to print the target calibration pattern corresponding to the target calibration axis, and send the target calibration image including the target calibration pattern to the host computer, and adjust the posture of the target calibration axis based on the target calibration angle.

[0046] In addition, to achieve the above-mentioned purpose, the present application also provides a medium, wherein the storage medium is a computer-readable storage medium, and a program for implementing the print head posture calibration method is stored on the computer-readable storage medium, and the program for implementing the print head posture calibration method is executed by a processor to implement the steps of the print head posture calibration method as described above.

[0047] The present application provides a method for calibrating the posture of a print head. The present application first controls the print head to print a target calibration pattern corresponding to a target calibration axis; obtains a target calibration image containing the target calibration pattern; calculates a target calibration angle of the target calibration axis based on the target calibration image, and adjusts the posture of the target calibration axis based on the target calibration angle. The present application accurately determines the target calibration angle based on the calibration image, realizes automatic calibration of the print head posture, and reduces the number of repeated adjustments required due to inaccurate adjustments. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0049] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0050] Figure 1 A schematic diagram of the hardware structure of the printing device for this application;

[0051] Figure 2 This is a flow chart of steps S10-S30 in an embodiment of a method for calibrating the posture of a print head of the present application;

[0052] Figure 3 A schematic diagram of the print head posture in an embodiment of the print head posture calibration method of the present application;

[0053] Figure 4 A schematic diagram of a calibration image in an embodiment of a method for calibrating the posture of a print head of the present application;

[0054] Figure 5 Fig. a is a schematic diagram of a method for calibrating the posture of a print head according to an embodiment of the present application in which the y-axis has no deviation;

[0055] Figure 5 b is a schematic diagram showing a deviation in the y-axis in an embodiment of the print head posture calibration method of the present application;

[0056] Figure 5 Figure c is a schematic diagram of the relationship between the ink droplet falling height and the landing point in an embodiment of the print head posture calibration method of the present application;

[0057] Figure 6 A schematic diagram of the calibration of the image acquisition module in an embodiment of the print head posture calibration method of the present application;

[0058] Figure 7 A schematic diagram of a simplified process of the print head posture calibration method of the present application;

[0059] Figure 8 A schematic diagram of the printing system for this application;

[0060] Fig. 9 This is a schematic diagram of the hardware structure of the electronic device involved in this application.

[0061] The purpose, features and advantages of this application will be further described in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0062] It should be understood that the specific embodiments described herein are only used to explain the technical solutions of the present application and are not used to limit the present application.

[0063] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0064] At present, the position of the print head of a printing device is prone to deviation from the standard position after the first installation or long-term use, which may cause abnormalities such as distortion, ghosting or stripes in the printed image. The print head adjustment method in the prior art usually controls the print head to print customized calibration patterns for three directions, and then manually observes the information of the calibration pattern to fine-tune the position of the print head. The above steps are then repeated continuously. However, the above solution requires manual determination of the adjustment angle and manual adjustment, resulting in low adjustment accuracy.

[0065] The main solution of the present application is: controlling the print head to print a target calibration pattern corresponding to the target calibration axis; obtaining a target calibration image containing the target calibration pattern; calculating the target calibration angle of the target calibration axis based on the target calibration image, so as to adjust the posture of the target calibration axis based on the target calibration angle. The present application accurately determines the target calibration angle based on the calibration image, thereby reducing the number of repeated adjustments required due to inaccurate adjustments.

[0066] It should be noted that the executor of this embodiment can be a printing system, or it can be an electronic device with data processing, network communication and program running functions, such as a tablet computer, a personal computer, a mobile phone, etc., or it can be a printing device that can realize the above functions, or it can be a host computer of a printing device. This embodiment does not make any specific limitations on this.

[0067] The present application embodiment provides a printing device, referring to Figure 1 The printing device 200 includes: a print head 210, a slide rail, a paper feed mechanism and a control circuit, etc., wherein the print head 210 is one of the key components in the printer, and is usually composed of many tiny nozzles. The slide rail is responsible for controlling the lateral movement of the print head 210 on the printing medium 220. The paper feed mechanism is responsible for the paper feeding and paper feeding process of the printing medium 220. The control circuit includes a main control circuit, a drive circuit, an input and output interface circuit and a detection circuit, etc., which is responsible for coordinating and controlling the mechanical devices of the printer.

[0068] The printing device 200 may be an inkjet printing device, which forms an image or text by ejecting ink onto a printing medium 220 through a nozzle 211 of a print head 210. The print head 210 of the inkjet printing device is composed of a plurality of columns of nozzles 211, each column of nozzles corresponding to a color channel. Optionally, the printing medium 220 includes, but is not limited to, film paper (such as PET film), paper, clothing, cloth, and other materials.

[0069] The movement direction of the print head 210 is usually perpendicular to the paper feed. In an inkjet printer, the print head 210 moves in the X-axis direction of the print medium, and the print medium moves in the Y-axis direction, so that the full page can be printed.

[0070] Based on this, the first embodiment of the present application proposes a method for calibrating the posture of a print head. The execution subject of the method for calibrating the posture may be a processor in a printing device or a processor in a host computer. Figure 1 The print head posture calibration method comprises steps S10 to S30:

[0071] Step S10, controlling the print head to print a target calibration pattern corresponding to the target calibration axis.

[0072] In this embodiment, the target calibration pattern is a printing pattern specially designed to determine the posture deviation of the print head on each target calibration axis. Different target calibration axes have different target calibration patterns, and these patterns have specific characteristics, which are convenient for analyzing and calculating the target calibration angle based on the collected calibration image. The print head is a component in the printing device used to eject ink droplets to form an image or pattern. The print head is composed of several columns of parallel print heads, and each column of print heads corresponds to a color. The print head here refers to a set of print heads corresponding to all different colors, or refers to the print head required to print each target calibration pattern.

[0073] As an optional implementation, the target calibration pattern is composed of lines, and according to the target calibration axis that needs to be calibrated currently, the print head is controlled to print the target calibration pattern corresponding to the target calibration axis. For example, if the target calibration axis is the x-axis, then a command is sent to let the print head print the target calibration pattern corresponding to the x-axis. After printing, the deviation of the print head in the x-axis direction is observed through the image acquisition module. Similarly, when the y-axis and the z-axis are calibrated, the corresponding target calibration patterns are also printed respectively.

[0074] Step S20: acquiring a target calibration image including the target calibration pattern.

[0075] In this embodiment, the target calibration image is an image containing a target calibration pattern printed out by an image acquisition module.

[0076] As an optional implementation, an image acquisition module is provided in the same track as the print head to acquire the target calibration image. Since the print head and the image acquisition module move in the same track, the field of view targeted by the image acquisition module is the content currently printed by the print head.

[0077] As another optional implementation, an image acquisition module disposed on the top shell of the printing device is used to acquire an image of the global field of view of the printing plane, and then a target calibration image containing a target calibration pattern is segmented from the image.

[0078] Step S30 , calculating a target calibration angle of the target calibration axis based on the target calibration image, so as to adjust the posture of the target calibration axis based on the target calibration angle.

[0079] In this embodiment, the target calibration angle is the angle that the target calibration axis needs to be calibrated, including the angle value and the tilt direction, so that the posture of the print head is restored to the standard posture, thereby ensuring the printing quality. The posture deviation of the print head in each target calibration axis is determined by analyzing the target calibration image, and then the target calibration angle is calculated.

[0080] It should be noted that the posture of the target calibration axis can be adjusted manually or automatically.

[0081] As an optional implementation, when the print head prints the target calibration pattern corresponding to the target calibration axis, the image acquisition module immediately captures the pattern to obtain a target calibration image. This target calibration image is analyzed and processed, for example, by comparing the difference between the target calibration pattern and the standard pattern in the target calibration image, and using image processing algorithms and mathematical models to calculate the posture deviation of the print head on the target calibration axis. Based on this deviation value, the angle that the print head needs to be adjusted in the axial direction is further calculated. If the print head deviates to the left by a certain angle in the x-axis direction, it is determined by calculation that a certain angle needs to be adjusted to the right to correct this deviation.

[0082] The present application first controls the print head to print a target calibration pattern corresponding to the target calibration axis; obtains a target calibration image containing the target calibration pattern; calculates a target calibration angle of the target calibration axis based on the target calibration image, and adjusts the posture of the target calibration axis based on the target calibration angle. The present application accurately determines the target calibration angle based on the calibration image, realizes automatic calibration of the print head posture, and reduces the number of repeated adjustments required due to inaccurate adjustments.

[0083] Based on any of the above embodiments, in a possible embodiment of the present application, before step S10, steps A10 to A30 are included:

[0084] Step A10, obtaining the calibration order of each calibration axis.

[0085] In this embodiment, refer to Figure 3 , the calibration sequence is the calibration order of each calibration axis. The calibration axis refers to the three coordinate axis directions of the print head in space, namely the x-axis, y-axis and z-axis. The U axis of the print head is parallel to the Y axis, the N axis of the print head is parallel to the X axis, and the V axis of the print head is parallel to the Z axis. These axes determine the position and posture of the print head. The calibration sequence is the order in which the different target calibration axes are calibrated when the print head is adjusting its posture. Among them, the y axis is the paper feeding direction, and the x axis is the reciprocating scanning printing direction. The x axis and the y axis constitute the printing plane.

[0086] The calibration order is not fixed in this application.

[0087] For example, the calibration order is z-axis, y-axis, and x-axis.

[0088] For example, the calibration order is z-axis, x-axis, y-axis.

[0089] For example, the calibration order is x-axis, z-axis, and y-axis.

[0090] For example, the calibration order is x-axis, y-axis, and z-axis.

[0091] For example, the calibration order is y-axis, x-axis, and z-axis.

[0092] For example, the calibration order is y-axis, z-axis, and x-axis.

[0093] As an optional implementation, the calibration order of the print head posture adjustment is first determined. For example, the x-axis can be calibrated first, then the y-axis, and finally the z-axis; or the z-axis can be calibrated first, then the x-axis and y-axis, etc.

[0094] Step A20, determining the target calibration axis according to the calibration sequence;

[0095] Step A30: calibrate each target calibration axis in turn according to the calibration sequence to obtain a target calibration angle corresponding to each target calibration axis.

[0096] In this embodiment, the calibration order of each calibration axis is obtained, and it is determined to calibrate the first axis, the second axis, and the third axis in sequence. Specifically, the print head is first controlled to print the target calibration pattern corresponding to the first axis, and then the image acquisition module is controlled to acquire a calibration image for the target calibration pattern, and then the target calibration angle of the first axis is determined according to the calibration image. If the target calibration angle of the first axis is less than the preset threshold, the print head is controlled to print the target calibration pattern corresponding to the second axis, and then the image acquisition module is controlled to acquire a target calibration image for the target calibration pattern, and then the target calibration angle of the second axis is determined according to the target calibration image. If the target calibration angle of the second axis is less than the preset threshold, the print head is controlled to print the target calibration pattern corresponding to the third axis, and then the image acquisition module is controlled to acquire a calibration image for the target calibration pattern, and then the target calibration angle of the third axis is determined according to the calibration image. If the target calibration angle of the third axis is less than the preset threshold, the calibration is completed.

[0097] For example, after long-term use of the printing device, the printed image has distortion and ghosting, and it is suspected that the position of the print head has deviated. The calibration order of this time is randomly determined to be the z-axis, x-axis, and y-axis. First, the print head is controlled to print the target calibration pattern corresponding to the z-axis. This target calibration pattern can be a combination of lines in the vertical direction of the printing plane, such as a series of vertical lines. After the print head prints the target calibration pattern of the z-axis, the image acquisition module shoots it to obtain the target calibration image. Analyzing this image, it is found that the print head is slightly higher in the z-axis direction. Through image processing and calculation, it is determined that the print head needs to be adjusted downward by a certain angle, such as 5 degrees. Then, according to the calibration order, the print head is controlled to print the target calibration pattern corresponding to the x-axis, such as a group of short horizontal lines arranged in the horizontal direction. For the x-axis, after the image acquisition module shoots the target calibration image of the x-axis target calibration pattern, it is analyzed and found that the print head is slightly offset to the right in the x-axis direction. After calculation, it is determined that it needs to be adjusted to the left by 3 degrees. Finally, the target calibration pattern corresponding to the y-axis is printed, such as a group of vertical lines. For the y-axis, similarly, by analyzing the y-axis calibration image, it is determined that the print head is tilted forward at a certain angle in the y-axis direction and needs to be adjusted back by 4 degrees. Finally, according to the calculated target calibration angle, the print head is automatically controlled to adjust its posture to improve the printing quality.

[0098] The present application first obtains the calibration order of each calibration axis, which includes the x-axis, y-axis and z-axis; controls the print head to print the target calibration pattern corresponding to each calibration axis according to the calibration order; determines the target calibration angle of the calibration axis based on the target calibration image captured based on the target calibration pattern, thereby realizing automatic calibration of the print head posture.

[0099] Based on any of the above embodiments, in a possible embodiment of the present application, if the target calibration axis is the z-axis, the step of controlling the print head to print the target calibration pattern corresponding to the target calibration axis includes the following steps S11 to S13:

[0100] Step S11, controlling all nozzles corresponding to each color in the print head to discharge ink to print a first target calibration sub-pattern.

[0101] In this embodiment, ink discharge refers to the action of the nozzle ejecting ink onto the printing plane. By controlling the nozzle to discharge ink, a specific pattern can be formed on the printing plane for calibrating the posture of the print head. The target calibration pattern corresponding to the z-axis is divided into two parts, a first target calibration sub-pattern and a second target calibration sub-pattern.

[0102] Control all the nozzles corresponding to each color to eject ink at the same time. For example, if the printing device has four nozzles of magenta, yellow, cyan and black, control all these nozzles of all colors to eject ink at the same time to form initial ink dots or lines on the printing plane.

[0103] Step S12, controlling the paper feeding mechanism to move the printing medium a first preset distance.

[0104] In this embodiment, the paper feed mechanism is a mechanical device that can accurately control the moving distance, and is used to control the movement of the printing medium in the printing device. By controlling the paper feed mechanism, the position of the printing medium on the printing plane can be accurately adjusted. The displacement direction of the printing medium is the y-axis in this embodiment. The printing medium refers to the material used in the printing process, such as paper, cloth, etc. During the print head calibration process, the printing medium needs to be moved to a specific position in order to print out the target calibration pattern. The first preset distance is a specific distance value set in advance, which is used to control the moving distance of the printing medium. This distance value is usually determined based on the calibration requirements and the characteristics of the printing device to ensure that the printed target calibration pattern can accurately reflect the posture deviation of the print head in the z-axis direction.

[0105] Sending a command to the paper feed mechanism control system to control the paper feed mechanism to move the print medium forward or backward by a first preset distance. For example, if the first preset distance is 5 mm, the paper feed mechanism is controlled to move the paper or other print medium forward or backward by 5 mm.

[0106] Step S13, controlling all the nozzles corresponding to each color to discharge ink to print the second target calibration sub-pattern, wherein the target calibration pattern corresponding to the z-axis includes the first target calibration sub-pattern and the second target calibration sub-pattern.

[0107] After the previous step is completed, the command is sent again to make all the nozzles corresponding to each color discharge ink again. This time, the ink discharge will form new ink dots or lines at the position after the print medium moves, that is, the second target calibration sub-pattern, which together with the first target calibration sub-pattern formed by the first ink discharge constitutes the target calibration pattern. For example, if the first ink discharge forms some vertical lines, the second ink discharge may form new lines below or above these vertical lines. By comparing the positional relationship of the two ink discharges, the position offset of the print head in the z-axis direction can be determined.

[0108] For example, refer to Figure 4The image corresponding to Rz in . It is detected that the print head calibration is required, and the target calibration axis is first determined to be the z-axis. Send instructions to the print head control system to make all nozzles corresponding to magenta, yellow, cyan, black and other colors discharge ink at the same time. On the printing plane, the ink droplets ejected by the nozzles of each color form some initial lines or patterns, which can be used as a reference for subsequent calibration. Then send instructions to the paper feed mechanism control system to control the paper feed mechanism to move the printing medium forward by 3 mm. The paper feed mechanism accurately moves the paper to the specified position to prepare for the next step of printing the second target calibration sub-pattern. After the printing medium moves to the new position, send instructions to the print head control system again to make all nozzles corresponding to each color discharge ink again. This time, the ink discharge forms a new pattern on the paper, which together with the pattern of the first ink discharge constitutes the target calibration pattern of the z-axis. The image acquisition module shoots the printed target calibration pattern and transmits the target calibration image to . By analyzing the positional relationship between the two ink discharges in the target calibration pattern, the height deviation of the print head in the z-axis direction is calculated. If it is found that the second ink-out pattern is offset upward by a certain distance compared to the first ink-out pattern, it is determined through calculation that the print head needs to be adjusted downward by a certain angle in the z-axis direction, and then an adjustment instruction is sent to the print head control system to adjust the print head to the correct posture to improve printing quality.

[0109] Since lines are used as target calibration patterns for z-axis calibration, the calibration efficiency and the efficiency of image acquisition and analysis are improved.

[0110] Based on any of the above embodiments, in a possible embodiment of the present application, the step of calculating the target calibration angle of the target calibration axis based on the target calibration image includes the following steps S31 to S33:

[0111] Step S31 : identifying the first line and the second line in the target calibration image.

[0112] In this embodiment, in the z-axis calibration, the target calibration image includes line patterns formed by two ink discharges from the nozzle, namely, a first target calibration sub-pattern and a second target calibration sub-pattern, which are used to determine the posture deviation of the print head in the z-axis direction. The first line is a line formed when the nozzle discharges ink for the first time. This line is used as a reference line for comparison with the line formed by the second ink discharge to determine the height change of the print head in the z-axis direction. The second line is a line formed when the nozzle discharges ink for the second time. By comparing with the first line, the posture deviation of the print head in the z-axis direction can be determined. The first target calibration sub-pattern includes a first line of each color, and the second target calibration sub-pattern includes a second line of each color.

[0113] The collected target calibration image is analyzed and processed. First, the first line and the second line are determined according to the color characteristics of the lines. The two ink discharges are performed simultaneously by all the print heads corresponding to each color. For example, if the printing device uses three print heads of magenta, yellow, and cyan, and the cyan print head is used in the two ink discharges, then in the calibration image, the first line and the second line of each color will be identified.

[0114] Step S32: extracting first feature points on the first line and second feature points on the second line of the same color.

[0115] In this embodiment, the feature points are key position points extracted from the first line and the second line of the same color for calculating the deviation of the print head posture. They include the first feature point on the first line and the second feature point on the second line. These feature points can be the endpoints, intersections, or pixels at specific positions of the lines. By determining the feature points, the relative position relationship between the lines can be analyzed more accurately, thereby calculating the deviation angle of the print head in the z-axis direction.

[0116] The feature points corresponding to the target calibration image are determined according to the positional relationship between the first line and the second line. For example, the midpoint, end point, etc. of the line are selected as the feature points. If the first line and the second line are parallel vertical lines, the upper end point or the lower end point of the line can be selected as the feature point. By determining these feature points, an accurate reference position can be provided for the subsequent calculation of the target calibration angle.

[0117] Exemplarily, the upper endpoint and the lower endpoint of the first line are selected as the first feature point, and the lower endpoint of the second line is selected as the second feature point.

[0118] Step S33: Calculate the target calibration angle of the z-axis according to the physical coordinates of the first feature point and the second feature point.

[0119] As an optional implementation, the target calibration angle of the print head in the z-axis direction is calculated based on the determined first feature point and the second feature point. For example, if the feature point is the endpoint of two lines, the deviation angle of the print head in the z-axis direction can be calculated by measuring the change in the distance between the two endpoints in the y-axis direction, combining the known parameters such as the print head height and the distance to the printing plane, and using mathematical knowledge such as trigonometric functions. Then, the angle value that needs to be adjusted is determined based on the deviation angle.

[0120] Exemplarily, all the nozzles corresponding to each color are controlled to discharge ink, and then the paper feed mechanism is controlled to move the printing medium by a first preset distance, and the nozzles are controlled to discharge ink again to form a target calibration pattern. The image acquisition module shoots the target calibration pattern to obtain a calibration image. The calibration image is analyzed, assuming that the printing device uses three colors of print heads, magenta, yellow, and cyan, and the cyan print head is used for both ink discharges. According to the color feature, the first line and the second line are determined to be cyan vertical lines. According to the positional relationship between the first line and the second line, the upper end point and the lower end point of the first line are selected as the first feature point, and the lower end point of the second line is selected as the second feature point. According to the target calibration image, the distance between the two points in the first feature point can be extracted, and then the distance between the upper end point in the first feature point and the second feature point is equal to the first preset distance moved by the printing medium, and the offset distance between the lower end point in the first feature point and the vertical direction can be extracted, so a triangle is formed according to the first feature point and the second feature point, and then the target calibration angle is calculated in combination with the above distance values.

[0121] As another optional implementation, the two endpoints of the first line and any endpoint of the second line are used as three feature points, that is, the physical coordinates of the feature points P0, P1, and P2 in the figure are extracted, and then a triangle is formed according to the three coordinates, thereby determining the offset angle of the first line relative to the y-axis as the target calibration angle.

[0122] For example, refer to Figure 4, according to the established z-axis calibration steps, all the nozzles corresponding to each color are controlled to discharge ink, and then the paper feed mechanism is controlled to move the printing medium by a first preset distance and then the nozzle is controlled to discharge ink again to form a target calibration pattern. The image acquisition module shoots the target calibration pattern to obtain a calibration image. The calibration image is analyzed to determine that the two vertical lines of cyan are the first line and the second line. Assuming that the first line is relatively clear and the position is easy to determine, the two endpoints P0 and P2 of the first line are accurately identified. Then determine an endpoint P1 of the second line. For example, the upper endpoint of the second line is selected as P1. In this way, the three points P0, P1, and P2 are determined as feature points. Through image analysis technology, the physical coordinates of these three feature points are accurately extracted. Assuming that in the image coordinate system, the coordinates of P0 are (x0, y0), the coordinates of P1 are (x1, y1), and the coordinates of P2 are (x2, y2). Construct a triangle based on the physical coordinates of the three feature points. With P0 and P2 as the two endpoints of the first line and P1 as any endpoint of the second line, a triangle ΔP0P1P2 is formed. The offset angle of the first line relative to the y-axis is calculated by the relationship between the side lengths of the triangle and trigonometric functions. Assume that by calculating the side lengths of the triangle, the lengths of |P0P1|, |P0P2|, and |P1P2| are c, b, and a respectively. According to the cosine theorem cosA=(b2+c2-a2) / (2bc), the angle of ∠P1P0P2 can be calculated. Then, based on this angle and the direction of the y-axis, the offset angle of the first line relative to the y-axis can be determined. If the calculated offset angle is a positive value, it means that the first line is offset to the right relative to the y-axis, and the print head may be too high in the z-axis direction, and the corresponding angle needs to be adjusted downward; if the offset angle is a negative value, it means that the first line is offset to the left relative to the y-axis, and the print head may be too low in the z-axis direction, and the corresponding angle needs to be adjusted upward. Assume that after calculation, the offset angle of the first line relative to the y-axis is 5 degrees, and it is determined that the print head needs to be adjusted downward by 5 degrees to restore to the standard posture and improve the printing quality.

[0123] By determining the first line and the second line and extracting feature points from these lines, the position change of the print head in the z-axis direction can be analyzed more accurately. Compared with the traditional manual observation method, this image analysis-based method can more accurately measure the tiny displacement between the lines, thereby improving the accuracy of calibration.

[0124] Based on any of the above embodiments, in a possible embodiment of the present application, if the target calibration axis is the y-axis, the step of controlling the print head to print the target calibration pattern corresponding to the target calibration axis includes:

[0125] Step S14, controlling all the nozzles corresponding to each color to discharge ink to print the target calibration pattern corresponding to the Y axis.

[0126] Reference Figure 4After determining that the target calibration axis is the y-axis, send instructions to the print head control system to make all the nozzles corresponding to each color eject ink at the same time. For example, if the printing device has four color nozzles of magenta, yellow, cyan, and black, control all these color nozzles to eject ink at the same time. After the ink is ejected, a number of vertical lines in the y-axis direction are formed on the printing plane, and the number of lines is the same as the number of columns of the nozzles.

[0127] Exemplarily, the current target calibration axis is determined to be the y-axis. Based on the instruction, the print head is controlled so that all nozzles corresponding to each color, such as magenta, yellow, cyan, and black, discharge ink at the same time. On the printing plane, the ink droplets ejected by the nozzles of each color form a plurality of vertical lines. For example, if there are nozzles of five colors, five vertical lines will be printed. The image acquisition module photographs the printed target calibration pattern and transmits the target calibration image to the processor. The processor determines the posture deviation of the print head in the y-axis direction by analyzing the uniformity of the spacing of these vertical lines. If it is found that some lines are bent in the y-axis direction or the line spacing is inconsistent, it means that the print head has a posture deviation in the paper feeding direction. After calculation, the angle that needs to be adjusted is determined, and then an adjustment instruction is sent to the print head control system to adjust the print head to the correct posture in the y-axis direction to improve the quality of subsequent poster printing.

[0128] Based on any of the above embodiments, in a possible embodiment of the present application, if the target calibration axis is the x-axis, the step of controlling the print head to print the target calibration pattern corresponding to the target calibration axis includes the following steps S25 to S26:

[0129] Step S25, determining the target nozzle corresponding to each color according to the preset number.

[0130] In this embodiment, the preset number is a number that is pre-set to identify a specific print head. In a printing device, the print heads are usually numbered for easy identification and control. For x-axis calibration, the specific print head that needs to participate in the calibration can be determined by the preset number. The target print head is a print head that is determined according to the preset number and is used to print the target calibration pattern. In the x-axis calibration, the target print head is usually a part of the print heads selected according to a certain rule, so as to more accurately detect the posture deviation of the print head in the x-axis direction.

[0131] Reference Figure 4 After determining that the target calibration axis is the x-axis, the target nozzles corresponding to each color are determined according to the preset numbering rule. For example, the preset numbering rule may be to select nozzles whose nozzle numbers are multiples of 10 as target nozzles. If the printing device has nozzles for four colors, namely magenta, yellow, cyan, and black, the nozzles that meet the conditions in each color are determined as target nozzles according to this rule.

[0132] Step S26, controlling the target nozzle of each color to discharge ink according to the arrangement order of each color, and controlling the print head to move a second preset distance along the x-axis while the target nozzle of each color discharges ink, so as to print the target calibration pattern corresponding to the x-axis.

[0133] In this embodiment, independent ink discharge means that each color target print head performs ink discharge operation independently, rather than all print heads discharge ink at the same time. In this way, the ink discharge situation of each color target print head in the x-axis direction can be more accurately controlled and observed, so as to detect the posture deviation of the print head in this direction. The second preset distance is the preset distance that the print head moves in the x-axis direction when discharging ink.

[0134] The target nozzles of each color are controlled in sequence to perform independent ink discharge operations. For example, the target nozzle in the magenta nozzle is first controlled to discharge ink and simultaneously move in the x-axis direction by a second preset distance, such as 10 mm. Then the target nozzle in the yellow nozzle is controlled to perform the same operation, and so on, the target nozzles of each color are subjected to ink discharge and movement operations. In this way, a number of horizontal lines are formed on the printing plane, with regular intervals between the lines. These lines are used as target calibration patterns for subsequent analysis of the posture deviation of the print head in the x-axis direction.

[0135] Optionally, after controlling the target nozzle corresponding to the current color to print ink, and before controlling the target nozzle corresponding to the next color to print ink, the print head posture calibration method further includes: controlling the print head not to print ink, and simultaneously controlling the print head to move a third preset distance along the x-axis.

[0136] In this embodiment, not ejecting ink means that the print head stops ejecting ink and is in an inoperative state. The third preset distance is the distance the print head moves after the target nozzle controlling the current color ejects ink and before the target nozzle controlling the next color ejects ink. This distance can be used to separate target calibration patterns of different colors or to prepare for subsequent calibration operations.

[0137] If the target nozzle corresponding to the current color has finished discharging ink, the print head is controlled to stop discharging ink. Then, the print head moves a third preset distance in the x-axis direction without discharging ink. This operation can ensure that there is a certain interval between target calibration patterns of different colors, which is convenient for subsequent image acquisition and analysis. At the same time, it can also avoid the interference of different colors of ink and affect the accuracy of calibration. Then enter the control process of the next color corresponding to the target nozzle to discharge ink.

[0138] Exemplarily, according to a preset numbering rule, the target nozzles corresponding to each color are determined. Assuming that the preset numbering rule is to select nozzles with nozzle numbers that are multiples of 10, and the printing device has nozzles of four colors: magenta, yellow, cyan, and black, then the nozzles numbered as multiples of 10 in each color are determined as target nozzles. First, the target nozzles in the magenta nozzles are controlled to discharge ink independently. While discharging ink, the print head moves a second preset distance, such as 10 mm, in the x-axis direction. In this way, magenta horizontal lines are formed on the printing plane. When the target nozzle in the magenta nozzle finishes discharging ink, the print head is controlled to stop discharging ink. Then, the print head moves a third preset distance, such as 5 mm, in the x-axis direction without discharging ink. This operation forms a blank area on the printing plane, separating the magenta target calibration pattern from the subsequent yellow target calibration pattern. Next, the target nozzle in the yellow nozzle is controlled to perform the same operation. The target nozzle in the yellow nozzle discharges ink and moves 10 mm in the x-axis direction, forming yellow horizontal lines on the printing plane. In the same way, the target nozzles in the cyan and black nozzles are controlled to discharge ink and move in sequence to form cyan and black horizontal lines respectively. Similarly, after the target nozzles of the yellow, cyan and black nozzles discharge ink, they are respectively controlled to stop discharging ink and move a third preset distance to ensure that there is a clear interval between the target calibration patterns of different colors.

[0139] Finally, the image acquisition module takes pictures of the printed target calibration patterns, determines the posture deviation of the print head in the x-axis direction by analyzing these target calibration patterns, calculates the target calibration angle, and adjusts the print head to improve the printing quality.

[0140] Based on any of the above embodiments, in a possible embodiment of the present application, if the target calibration axis is an x-axis or a y-axis, the target calibration pattern includes a target line, and the step of calculating the target calibration angle of the target calibration axis based on the target calibration image includes the following steps S34 to S38:

[0141] Step S34, determining at least three target lines and at least two target line pairs in the target calibration image, wherein the target line pairs include two target lines.

[0142] In this embodiment, the target lines are parallel lines extracted from the target calibration image, and the target line pair includes two target lines.

[0143] As an optional implementation, at least three target lines are extracted from the target calibration image, and at least two target line pairs are formed based on the target lines.

[0144] Exemplarily, a first target line, a second target line and a third target line are extracted, and then a first target line pair is formed based on the first target line and the second target line, and a second target line pair is formed based on the second target line and the third target line.

[0145] Exemplarily, a first target line, a second target line, a third target line and a fourth line are extracted, and then a first target line pair is formed based on the first target line and the second target line, and a second target line pair is formed based on the third target line and the fourth target line.

[0146] Step S35, obtaining a first distance and a second distance according to the distance between two target lines in the at least two target line pairs.

[0147] In this embodiment, after determining at least two target line pairs, the distance between two target lines in each target line pair is determined. For the two target line pairs, a first distance of the first target line pair and a second distance of the second target line pair are obtained.

[0148] Step S36: determining the tilt direction on the target calibration axis according to the magnitude relationship between the first distance and the second distance.

[0149] In this embodiment, the tilt direction is the offset direction of the print head on the target calibration axis, for example, a positive tilt or a negative tilt relative to the target calibration axis.

[0150] As an optional implementation, along the positive direction of the target calibration axis, the first distance is in the negative direction of the second distance. If the first distance is greater than the second distance, the tilt direction is negative; if the first distance is less than the second distance, the tilt direction is positive. This is because the ink droplets drip in a nearly parabolic manner due to the influence of gravity g and the angle of injection. As the z value decreases, the change in x value per unit of fixed z value decreases, so the projected length of the nozzle spacing at a higher position is smaller than the projected length at a lower position. Therefore, in the first distance and the second distance, the side of the print head corresponding to the smaller value is higher relative to the printing plane.

[0151] Step S37, determining a tilt angle value according to the first distance, the second distance and a reference distance.

[0152] Step S38: determining the target calibration angle based on the tilt direction and the tilt angle value.

[0153] In this embodiment, the tilt angle value is a numerical value of the tilt angle.

[0154] It should be noted that, taking the y-axis as an example, refer to Figure 5In a, when there is no y-axis installation deviation, the distances d1' and d1'' between the first and second columns and the third and fourth columns printed should be equal to the physical distance d1 between the corresponding nozzle rows on the print head; when there is a y-axis deviation, refer to Figure 5 In b, the distances d1' and d1'' between the first and second columns and the third and fourth columns printed are the projections of d on the x-axis. According to the captured Ry calibration image, the values of d1' and d1'' can be detected, and θ1 = arccos(d1’ / d1), θ2 = arccos(d1” / d1) can be obtained; refer to Figure 5 In c, due to the influence of gravity g and the spraying angle, the ink droplets drip in an almost parabolic manner. It can be seen that as the z value decreases, the change amount of the x value per unit fixed z value unit decreases. Therefore, the projected length of the nozzle spacing at a higher position is less than that at a lower position, that is Figure 2 d1' < d1''; by comparing the magnitudes of d1' and d1'', the tilting direction of the nozzle can be judged. Considering that the spacing projection at a higher position is less affected by the spraying angle, therefore, by comparing θ1 and θ2, the smaller angle value is taken as the tilting angle value of the y-axis.

[0155] As an alternative implementation, calculate a first ratio of the first distance to the reference distance, and a second ratio of the second distance to the reference distance; determine a first angle according to the first ratio, and determine a second angle according to the second ratio; if the first angle is less than the second angle, then take the first angle as the tilting angle value; if the first angle is greater than the second angle, then take the second angle as the tilting angle value.

[0156] If the target calibration axis is the y-axis. The target line is a specific line selected from the calibration image for determining the posture deviation of the print head in the Y-axis direction. Since lines of different colors may have different deviations during the printing process, at least three target lines of different colors need to be selected for analysis. The acquired Y-axis calibration image is analyzed and processed. According to the color characteristics of the lines, at least three target lines of different colors are determined from the calibration image. For example, if the printing device has four color nozzles of magenta, yellow, cyan, and black, then vertical lines of magenta, yellow, cyan, and black can be selected as target lines. Or vertical lines of magenta, yellow, and cyan can be selected as target lines. Measure the distance between adjacent target lines. For example, measure the distance between the magenta line and the yellow line, and the distance between the yellow line and the cyan line. If the distance between adjacent lines is uneven in the Y-axis direction, it means that the print head is tilted in the Y-axis direction. If the distance gradually increases, it means that the print head is tilted to the right; if the distance gradually decreases, it means that the print head is tilted to the left. According to the change in the distance between adjacent lines, the mathematical model and algorithm are used to calculate the target calibration angle of the print head in the Y-axis direction. For example, if it is found that the distance between the magenta line and the yellow line is 2 mm larger than the standard distance, and the distance between the yellow line and the cyan line is 3 mm larger than the standard distance, the deviation angle of the print head in the Y-axis direction can be calculated based on these distance changes, combined with known parameters such as the print head height and the distance to the printing plane, and mathematical knowledge such as trigonometric functions. Then, the angle value that needs to be adjusted is determined based on the deviation angle.

[0157] Exemplarily, all nozzles corresponding to each color are controlled to discharge ink, and a number of vertical lines parallel to the Y axis are printed. The image acquisition module shoots the target calibration pattern to obtain a calibration image. According to the color characteristics, the magenta, yellow and cyan vertical lines are determined from the calibration image as the target lines. The distance between the magenta line and the yellow line is measured to be d1 mm, and the distance between the yellow line and the cyan line is d2 mm. Since d1 is less than d2, that is, since the distance gradually increases, it means that the print head is tilted to the right. According to these distance changes, the reference distance d is obtained. The first ratio d1 / d is determined, and the second ratio d2 / d is determined. Then the first angle θ1=arccos(d1 / d) and θ2=arccos(d2 / d) are determined. Since θ1 is less than θ2, θ1 is used as the tilt angle value. Combined with the known parameters, it is calculated that the deviation angle of the print head in the Y-axis direction is 4 degrees, and the tilt direction is negative. Therefore, the print head needs to be adjusted 4 degrees in the positive direction to restore to the standard posture.

[0158] For example, refer to Figure 4, control all the nozzles corresponding to each color to eject ink, and print several vertical lines parallel to the Y-axis. The image acquisition module takes a picture of the target calibration pattern to obtain a calibration image. Determine the cyan, magenta, yellow, and black lines as target lines in sequence from left to right. Measure the distance between the cyan and magenta lines as d1. Through image analysis technology, accurately measure the value of d1 as 12 mm. Measure the distance between the yellow and black lines as d2. Measure the value of d2 as 14 mm. When the print head is installed without deviation, the distance between different columns should be the actual physical pitch value of the print head, that is, the reference distance d. Due to the influence of gravity g, the higher the drop point of the print head, the farther the actual drop point is compared to the lower drop point. If d1 < d2, it means that the drop points of the print heads corresponding to the cyan and magenta lines are relatively low, and the drop points of the print heads corresponding to the yellow and black lines are relatively high. The print head has a tendency to tilt upward in the Y-axis direction, and the tilt direction is the positive direction. If d1 > d2, it means that the drop points of the print heads corresponding to the cyan and magenta lines are relatively high, and the drop points of the print heads corresponding to the yellow and black lines are relatively low. The print head has a tendency to tilt downward in the Y-axis direction, and the tilt direction is the negative direction. According to the specific values of d1 and d2 and the known physical pitch d of the print head, use mathematical knowledge such as trigonometric functions to calculate the deviation angle of the print head in the Y-axis direction. Determine the first ratio d1 / d, and determine the second ratio d2 / d. Further determine the first angle θ1 = arccos(d1 / d), θ2 = arccos(d2 / d).

[0159] For example, assume that the calculated deviation angle is 5 degrees. If the print head tilts upward in the Y-axis direction, that is, the tilt direction is the positive direction, then determine that the print head needs to be adjusted downward by 5 degrees to restore to the standard pose; if the print head tilts downward in the Y-axis direction, that is, the tilt direction is the negative direction, then determine that the print head needs to be adjusted upward by 5 degrees.

[0160] Through this embodiment, the tilt direction of the print head in the Y-axis direction can be accurately judged using the distance relationship of the four target lines, and the target calibration angle can be calculated, so as to achieve precise calibration of the print head pose and improve the printing quality.

[0161] Similarly, if the target calibration axis is the x-axis, the calibration image is an image obtained by photographing the printed x-axis target calibration pattern through the image acquisition module. In the x-axis calibration, the calibration image contains several rows of lines parallel to the x-axis, the lines in the same row have different colors, and the parallel lines in each column have the same color. The target line is a specific line selected from the calibration image to determine the posture deviation of the print head in the x-axis direction. Since the lines in the same column have the same color, the target lines should have the same color in the x-axis calibration. Selecting at least three target lines of the same color for analysis can more accurately determine the deviation of the print head in the x-axis direction. Analyze and process the collected x-axis calibration image. According to the color characteristics of the lines, determine at least three target lines of the same color from the calibration image. For example, if the printing device has four colors of magenta, yellow, cyan, and green print heads, then three parallel magenta lines can be selected as target lines. At this time, the tilt direction is the offset direction of the print head in the x-axis direction, which can be forward tilt or backward tilt. By analyzing the distance change between adjacent target lines, the tilt direction of the print head in the x-axis direction can be determined. The target calibration angle is the angle value that needs to be adjusted in the X-axis direction of the print head so that the print head's posture returns to the standard posture to ensure the printing quality. By calculating the distance change between adjacent target lines, the deviation angle of the print head in the X-axis direction can be determined, and then the angle that needs to be adjusted can be calculated. Measure the distance between adjacent target lines. For example, measure the distance between three magenta lines. If the distance between adjacent lines is uneven in the X-axis direction, it means that the print head is tilted in the X-axis direction. If the distance gradually increases, it means that the print head is tilted backward; if the distance gradually decreases, it means that the print head is tilted forward. According to the distance change between adjacent lines, the target calibration angle of the print head in the X-axis direction is calculated using mathematical models and algorithms. For example, if it is found that the distance between the three magenta lines is d1 mm and d2 mm respectively, the deviation angle of the print head in the X-axis direction can be calculated based on these distance changes, combined with known parameters such as the print head width and the distance of the printing plane, and mathematical knowledge such as trigonometric functions. Then, the angle value that needs to be adjusted is determined based on the deviation angle.

[0162] Exemplarily, according to the preset numbering rule, determine the target print head corresponding to each color. Then, sequentially control the target print head of each color to independently eject ink, and while ejecting ink, move a second preset distance in the X-axis direction to print a number of lines parallel to the X-axis. The image acquisition module takes a picture of the target calibration pattern to obtain a calibration image. According to the color characteristics, three magenta parallel lines are determined from the calibration image as the target lines. The distances between the three magenta lines are measured as d1 millimeters and d2 millimeters in sequence. Since the distances are gradually increasing, it indicates that the print head is tilted in the negative direction. Based on these distance changes and combined with the known parameters, the deviation angle of the print head in the X-axis direction is calculated to be -3 degrees. Therefore, the print head needs to be adjusted 3 degrees in the negative direction to restore to the standard pose.

[0163] Exemplarily, refer to Figure 4 , according to the preset numbering, determine the target print head corresponding to each color, sequentially control the target print head of each color to independently eject ink, and while ejecting ink, move a second preset distance in the X-axis direction to print a number of lines parallel to the X-axis. The image acquisition module takes a picture of the target calibration pattern to obtain a calibration image. Four cyan lines are selected from the calibration image as the target lines, specifically the first two and the last two at the head. The distance between the first two cyan lines at the head is measured as d1. Assume that through image analysis technology, the value of d1 is accurately measured to be 8 millimeters. The distance between the last two cyan lines at the tail is measured as d2. Assume that the measured value of d2 is 10 millimeters. If d1 < d2, it indicates that the print head has a tendency to tilt backward in the X-axis direction. This is because if the print head tilts backward, the line spacing at the tail will relatively increase. If d1 > d2, it indicates that the print head has a tendency to tilt forward in the X-axis direction. Similarly, if the print head tilts forward, the line spacing at the head will relatively increase. According to the specific values of d1 and d2 and the known print head parameters, the deviation angle of the print head in the X-axis direction can be calculated using mathematical knowledge such as trigonometric functions. Similar to the calculation scheme for the Y-axis, it will not be elaborated here.

[0164] Given some relevant dimensional parameters of the print head, when d1 = 8 millimeters and d2 = 10 millimeters, the calculated deviation angle is 4 degrees. If the print head tilts backward in the X-axis direction, then it is determined that the print head needs to be adjusted 4 degrees forward to restore to the standard pose; if the print head tilts forward in the X-axis direction, then it is determined that the print head needs to be adjusted 4 degrees backward.

[0165] Through this embodiment, the tilt direction of the print head in the X-axis direction can be accurately judged using the four cyan target lines, and the target calibration angle can be calculated, thereby achieving precise calibration of the print head pose and improving the printing quality.

[0166] Since the tilt direction and target calibration angle of the print head can be accurately determined, the number of repeated adjustments due to inaccurate adjustments is reduced. One adjustment can bring the print head close to the standard posture, saving time and resources and improving the efficiency of equipment use.

[0167] Based on any of the above embodiments, in a possible embodiment of the present application, before step S10, the calibration method further includes:

[0168] Step B10, calibrate the image acquisition module.

[0169] As an optional implementation, refer to Figure 6 , use the printed plane as the calibration plate, that is, the calibration plate needs to cover the entire field of view of the image acquisition module, and the physical size of the calibration plate is obtained from the database. Capture the calibration plate image from multiple angles and positions to ensure that the image contains different postures of the calibration plate. Use the image processing algorithm to extract the pixel coordinates (x, y) of the feature points of the calibration plate, and record the corresponding world coordinate system coordinates (xw, yw, 0). Calculate the internal parameters of the image acquisition module, the internal parameter matrix: contains parameters such as focal length (fx, fy), principal point offset (cx, cy), etc., describing the mapping relationship between the pixel coordinate system and the camera coordinate system (xc, yc, zc). Distortion coefficient: correct the radial distortion (k1, k2) and tangential distortion (p1, p2) of the lens. Then perform external parameter calibration, calculate the rotation matrix R and translation vector T, and transform the world coordinate system (xw, yw, zw) to the camera coordinate system (xc, yc, zc). For the plane calibration plate (zw=0), the homography matrix H is used to simplify the calculation. Through the intrinsic matrix K, extrinsic parameters R and T, a projection model from pixel coordinates to world coordinates is constructed: the formula is: s*[x,y,1]^T=K*[R|T]*[xw,yw,0,1]^T, where s is the scale factor. Then, the mapping relationship between pixel points and the world coordinates of the printing plane is derived through inverse transformation.

[0170] Based on any of the above embodiments, in a possible embodiment of the present application, after the step of calculating the target calibration angle of the target calibration axis based on the target calibration image, it includes: if the absolute value of the target calibration angle is greater than a preset threshold, adjusting the posture of the target calibration axis based on the target calibration angle.

[0171] In this embodiment, the preset threshold is a pre-set angle value used to determine whether the deviation of the print head on a certain target calibration axis needs to be adjusted. If the target calibration angle is greater than the preset threshold, the print head posture needs to be adjusted; if the target calibration angle is not greater than the preset threshold, it is considered that the posture deviation of the print head on this axis is within an acceptable range and no further adjustment is required. The print head posture is the position and direction of the print head in three-dimensional space, including the position and tilt angle in the three directions of the x-axis, y-axis and z-axis. By adjusting the print head posture, the inkjet position of the print head can be made more accurate and the printing quality can be improved.

[0172] As an optional implementation, according to the method described in the previous embodiment, the target calibration angle of each target calibration axis is determined according to the calibration image collected by the target calibration pattern. For each target calibration axis, the determined target calibration angle is compared with a preset threshold. If the target calibration angle is greater than the preset threshold, the next step is executed; if the target calibration angle is not greater than the preset threshold, the calibration of the axis is considered to be completed, and the calibration of the next target calibration axis is entered. If the target calibration angle is greater than the preset threshold, an instruction is sent to the print head control system according to the target calibration angle to adjust the posture of the print head in the axis. The adjustment method can be to adjust the position or angle of the print head by a mechanical device, or to adjust the posture of the print head by controlling the inkjet parameters of the print head by software. After adjusting the posture of the print head, the calibration image is collected again to determine the target calibration angle of the target calibration axis. If the target calibration angle is still greater than the preset threshold, the above steps are repeated until the target calibration angle is not greater than the preset threshold. When the target calibration angle is not greater than the preset threshold, the calibration of the axis is considered to be completed, and the calibration of the next target calibration axis is entered. According to the above steps, the three target calibration axes of x-axis, y-axis and z-axis are calibrated until the target calibration angles of the three axes are no greater than the preset threshold, thus completing the posture calibration of the entire print head.

[0173] Exemplarily, first determine that the target calibration axis is the z-axis, control the print head to print the target calibration pattern corresponding to the z-axis, collect the calibration image and determine the target calibration angle. Assume that the calculated target calibration angle is 3 degrees. The preset threshold is set to 2 degrees. Since the target calibration angle is greater than the preset threshold, the print head posture is adjusted according to the target calibration angle. Print the target calibration pattern again, collect the calibration image to determine the target calibration angle. Assume that the target calibration angle is 1.5 degrees this time, which is less than the preset threshold, and the z-axis calibration is completed. Then perform the y-axis calibration and determine that the target calibration angle is 2.5 degrees. The preset threshold is still 2 degrees, the target calibration angle is greater than the preset threshold, and the print head posture is adjusted. Repeat the calibration until the target calibration angle is less than the preset threshold. Assume that after two adjustments, the target calibration angle is 1 degree, and the y-axis calibration is completed. Finally, perform the x-axis calibration and determine that the target calibration angle is 2 degrees. The preset threshold is 2 degrees, the target calibration angle is equal to the preset threshold, and it can be considered that no further adjustment is required, and the x-axis calibration is completed. At this point, the calibration of the three axes is completed, the print head posture of the printing device is accurately adjusted, and the printing quality is improved.

[0174] By setting a preset threshold, you can ensure that the posture deviation of the print head on each target calibration axis is within an acceptable range. If the target calibration angle is greater than the preset threshold, continue to calibrate until the target calibration angle is no greater than the preset threshold, thereby improving the accuracy of the calibration. The repeated calibration process can gradually reduce the posture deviation of the print head, making the position and angle of the print head more accurate and improving the print quality. The entire calibration process is automatically controlled, from determining the target calibration angle to adjusting the print head posture, and then to repeated calibration, all can be completed automatically without manual intervention, improving the efficiency and automation of calibration.

[0175] For example, in order to help understand the technical concept or technical principle of the print head posture calibration method after the above embodiments are combined, please refer to Figure 7 , Figure 7 A brief flow chart of a print head posture calibration method is provided, as follows:

[0176] Taking the calibration sequence of z-axis, y-axis and x-axis as an example, the print head of the printing device is composed of several parallel columns of print heads, and each column of print heads corresponds to one color. After long-term high-intensity printing operations, the printing quality has declined. It is suspected that the print head posture has deviated and needs to be calibrated. Relative to the printing plane, the x-axis is the reciprocating movement direction of the print head, and the y-axis is the paper feeding direction, that is, each column of print heads is arranged in the y-axis direction. Determine to calibrate the z-axis first. At this time, control all print heads to discharge ink at the same time, and print several vertical lines in the y-axis direction on the printing plane. The number is the same as the number of columns of print heads, that is, the number of colors. For example, if the device has five colors of print heads, it will print five vertical lines. Next, control the y-axis paper feeding stepping movement once, and then control all print heads to discharge ink at the same time again to print the second round of vertical lines. The image acquisition module shoots the printed pattern to obtain a calibration image. Analyze the relative position change of the two rounds of vertical lines in the y-axis direction, calculate the target calibration angle of the print head in the z-axis direction through image processing algorithms and mathematical models, if the target calibration angle is greater than the preset threshold, adjust the print head posture in the z-axis based on the target calibration angle; if the target calibration angle is not greater than the preset threshold, it is considered that the calibration of this axis is completed, and enter the calibration of the y-axis. After completing the z-axis calibration, start the y-axis calibration. Similarly, control all print heads to discharge ink at the same time, and print several vertical lines in the y-axis direction again, the number of which is consistent with the number of print head columns. After the image acquisition module captures the calibration image, analyze the straightness and spacing uniformity of these vertical lines. If it is found that some lines have inconsistent line spacing in the y-axis direction, it means that the print head has a posture deviation in the y-axis in the paper feeding direction. Then determine the target calibration angle of the y-axis according to the calibration pattern corresponding to the target calibration pattern. If the target calibration angle is greater than the preset threshold, adjust the print head posture in the y-axis based on the target calibration angle; if the target calibration angle is not greater than the preset threshold, it is considered that the calibration of this axis is completed, and enter the calibration of the x-axis. Finally, perform the x-axis calibration. First, control the print heads in the first column that are multiples of 10 to eject ink at the same time, and keep the inkjet moving a fixed distance (10mm) in the x direction, leaving a 5mm space. Assume that the print heads numbered 10, 20, and 30 in the first column eject ink, and after moving, a horizontal line and a blank are formed. Then perform the same action on the remaining columns of print heads in turn. In this way, several rows of horizontal lines will appear on the printing plane, with regular intervals between the lines. After the image acquisition module captures the calibration image, it then determines the target calibration angle of the x-axis based on the calibration pattern corresponding to the target calibration pattern. If the target calibration angle is greater than the preset threshold, the print head posture on the x-axis is adjusted based on the target calibration angle; if the target calibration angle is not greater than the preset threshold, it is considered that the calibration of the axis is completed.

[0177] The present application also provides a printing system. Figure 8The printing system includes: a host computer and an inkjet printing device, and the host computer is communicatively connected with the inkjet printing device.

[0178] The host computer is used to obtain the target calibration angle of the target calibration axis based on the print head posture calibration method described in any of the above embodiments, and send the target calibration angle to the inkjet printing device; the inkjet printing device is used to control the print head to print the target calibration pattern corresponding to the target calibration axis, and send the target calibration image including the target calibration pattern to the host computer, and adjust the posture of the target calibration axis based on the target calibration angle.

[0179] The printing system provided in the embodiment of the present application adopts the print head posture calibration method in the above embodiment, which can solve the technical problem that the adjustment angle needs to be determined manually and adjusted manually, resulting in low adjustment accuracy. Compared with the prior art, the beneficial effects of the printing system provided in the embodiment of the present application are the same as the beneficial effects of the print head posture calibration method provided in the above embodiment, and other technical features of the printing system are the same as the features disclosed in the above embodiment method, which will not be repeated here.

[0180] The present application provides an electronic device, which includes: at least one processor; and a memory that is communicatively connected to the at least one processor; wherein the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the print head posture calibration method in the above-mentioned embodiment one.

[0181] Reference below Fig. 9 , which shows a schematic diagram of the structure of an electronic device suitable for implementing an embodiment of the present application. The electronic device in the embodiment of the present application may be a host computer or an inkjet printing device. When the electronic device is a host computer, its form may include but is not limited to terminals such as mobile terminals, laptop computers, tablet computers, etc., and fixed terminals such as desktop computers, etc. Fig. 9 The electronic device shown is merely an example and should not bring any limitation to the functions and scope of use of the embodiments of the present application.

[0182] like Fig. 9As shown, the electronic device may include a processing device 1001 (e.g., a central processing unit, a graphics processor, etc.), which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM: Read Only Memory) 1002 or a program loaded from a storage device 1003 to a random access memory (RAM: Random Access Memory) 1004. In RAM1004, various programs and data required for the operation of the electronic device are also stored. The processing device 1001, ROM1002, and RAM1004 are connected to each other through a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Generally, the following systems can be connected to the I / O interface 1006: an input device 1007 including, for example, a touch screen, a touch pad, a keyboard, a mouse, an image sensor, a microphone, an accelerometer, a gyroscope, etc.; an output device 1008 including, for example, a liquid crystal display (LCD: Liquid Crystal Display), a speaker, a vibrator, etc.; a storage device 1003 including, for example, a magnetic tape, a hard disk, etc.; and a communication device 1009. The communication device 1009 can allow the electronic device to communicate with other devices wirelessly or by wire to exchange data. Although the figure shows an electronic device with various systems, it should be understood that it is not required to implement or have all the systems shown. More or fewer systems can be implemented or have alternatively.

[0183] In particular, according to the embodiments disclosed in the present application, the process described above with reference to the flowchart can be implemented as a computer software program. For example, the embodiments disclosed in the present application include a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program includes a program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network through a communication device, or installed from a storage device 1003, or installed from a ROM 1002. When the computer program is executed by the processing device 1001, the above-mentioned functions defined in the method of the embodiment disclosed in the present application are executed.

[0184] The electronic device provided by the present application adopts the print head posture calibration method in the above embodiment, which can solve the technical problem that the adjustment angle needs to be determined manually and adjusted manually, resulting in low adjustment accuracy. Compared with the prior art, the beneficial effects of the electronic device provided by the present application are the same as the beneficial effects of the electronic device provided by the above embodiment, and other technical features in the electronic device are the same as the features disclosed in the method of the previous embodiment, which will not be repeated here.

[0185] It should be understood that the various parts disclosed in this application can be implemented by hardware, software, firmware or a combination thereof. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0186] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0187] The present application provides a computer-readable storage medium having computer-readable program instructions (ie, computer programs) stored thereon, and the computer-readable program instructions are used to execute the print head posture calibration method in the above-mentioned embodiment.

[0188] The computer-readable storage medium provided in the present application may be, for example, a USB flash drive, but is not limited to electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, systems or devices, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In this embodiment, the computer-readable storage medium may be any tangible medium containing or storing a program that may be used by or in conjunction with an instruction execution system, system, or device. The program code contained on the computer-readable storage medium may be transmitted using any appropriate medium, including, but not limited to, wires, optical cables, RF (Radio Frequency), etc., or any suitable combination thereof.

[0189] The computer-readable storage medium may be included in the printing device; or may exist independently without being installed in the printing device.

[0190] The above-mentioned computer-readable storage medium carries one or more programs. When the above-mentioned one or more programs are executed by the printing device, the printing device can implement the following steps: control the print head to print a target calibration pattern corresponding to the target calibration axis; obtain a target calibration image containing the target calibration pattern; calculate the target calibration angle of the target calibration axis based on the target calibration image, so as to adjust the posture of the target calibration axis based on the target calibration angle.

[0191] Computer program code for performing the operations of the present application may be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0192] The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, function and operation of the system, method and computer program product according to various embodiments of the present application. In this regard, each square box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the square box can also occur in a sequence different from that marked in the accompanying drawings. For example, two square boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each square box in the block diagram and / or flow chart, and the combination of the square boxes in the block diagram and / or flow chart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0193] The modules involved in the embodiments described in this application may be implemented by software or hardware, wherein the name of the module does not constitute a limitation on the unit itself in some cases.

[0194] The readable storage medium provided by the present application is a computer-readable storage medium, which stores computer-readable program instructions (i.e., computer programs) for executing the above-mentioned print head posture calibration method, and can solve the technical problem of low adjustment accuracy caused by the need for manual determination of the adjustment angle and manual adjustment. Compared with the prior art, the beneficial effects of the computer-readable storage medium provided by the present application are the same as the beneficial effects of the print head posture calibration method provided by the above-mentioned embodiment, and will not be repeated here.

[0195] An embodiment of the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the steps of the above-mentioned method for calibrating the posture of the print head.

[0196] The computer program product provided by the present application can solve the technical problem that the adjustment angle needs to be determined manually and adjusted manually, resulting in low adjustment accuracy. Compared with the prior art, the beneficial effects of the computer program product provided by the embodiment of the present application are the same as the beneficial effects of the print head posture calibration method provided by the above embodiment, which will not be repeated here.

[0197] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent processing scope of the present application.

Claims

1. A method for calibrating the posture of a print head, characterized in that: The posture calibration method comprises: Controlling the print head to print a target calibration pattern corresponding to the target calibration axis; Acquire a target calibration image including the target calibration pattern; A target calibration angle of the target calibration axis is calculated based on the target calibration image to adjust the posture of the target calibration axis based on the target calibration angle.

2. The method for calibrating the print head posture as claimed in claim 1, characterized in that: If the target calibration axis is the z-axis, the step of controlling the print head to print a target calibration pattern corresponding to the target calibration axis includes: Controlling all nozzles corresponding to each color in the print head to discharge ink to print a first target calibration sub-pattern; Controlling the paper feeding mechanism to move the printing medium by a first preset distance; All the nozzles corresponding to each color are controlled to discharge ink to print a second target calibration sub-pattern, and the target calibration pattern corresponding to the z-axis includes the first target calibration sub-pattern and the second target calibration sub-pattern.

3. The method for calibrating the print head posture as claimed in claim 2, characterized in that: The first target calibration sub-pattern includes first lines of each color, the second target calibration sub-pattern includes second lines of each color, and the step of calculating the target calibration angle of the target calibration axis based on the target calibration image includes: identifying the first line and the second line in the target calibration image; Extracting first feature points on the first line and second feature points on the second line of the same color; A target calibration angle of the z-axis is calculated according to the physical coordinates of the first feature point and the second feature point.

4. The method for calibrating the print head posture as claimed in claim 1, characterized in that: If the target calibration axis is the y-axis, the step of controlling the print head to print a target calibration pattern corresponding to the target calibration axis includes: All the nozzles corresponding to each color are controlled to discharge ink to print the target calibration pattern corresponding to the Y axis.

5. The method for calibrating the posture of a print head according to claim 1, wherein: If the target calibration axis is the x-axis, the step of controlling the print head to print a target calibration pattern corresponding to the target calibration axis includes: Determine the target nozzle corresponding to each color according to the preset number; The target nozzles of each color are controlled to discharge ink according to the arrangement order of each color, and the print head is controlled to move a second preset distance along the x-axis while the target nozzles of each color discharge ink, so as to print the target calibration pattern corresponding to the x-axis.

6. The method for calibrating the posture of a print head according to claim 5, wherein: After controlling the target nozzle corresponding to the current color to discharge ink, and before controlling the target nozzle corresponding to the next color to discharge ink, the print head posture calibration method further includes: The print head is controlled not to output ink, and at the same time, the print head is controlled to move a third preset distance along the x-axis.

7. The method for calibrating the posture of a print head according to claim 4 or 5, characterized in that: The target calibration pattern includes a target line, and the step of calculating the target calibration angle of the target calibration axis based on the target calibration image includes: Determining at least three target lines and at least two target line pairs in the target calibration image, wherein the target line pairs include two target lines; Obtaining a first distance and a second distance according to a distance between two target lines in the at least two target line pairs; Determining a tilt direction on the target calibration axis according to a magnitude relationship between the first distance and the second distance; Determine a tilt angle value according to the first distance, the second distance and a reference distance; The target calibration angle is determined based on the tilt direction and the tilt angle value.

8. The method for calibrating the posture of a print head according to claim 7, wherein: Along the positive direction of the target calibration axis, the first distance is in the negative direction of the second distance, and the step of determining the tilt direction on the target calibration axis according to the magnitude relationship between the first distance and the second distance comprises: If the first distance is greater than the second distance, the tilt direction is negative; If the first distance is smaller than the second distance, the tilt direction is positive.

9. The method for calibrating the posture of a print head according to claim 7, wherein: The step of determining the tilt angle value according to the first distance, the second distance and a reference distance comprises: Calculating a first ratio of the first distance to the reference distance, and a second ratio of the second distance to the reference distance; determining a first angle according to the first ratio, and determining a second angle according to the second ratio; If the first angle is smaller than the second angle, the first angle is used as the tilt angle value; If the first angle is greater than the second angle, the second angle is used as the tilt angle value.

10. The method for calibrating the posture of a print head according to any one of claims 1 to 9, characterized in that: Before the step of controlling the print head to print the target calibration pattern corresponding to the target calibration axis, the method includes: Get the calibration order of each calibration axis; determining the target calibration axis according to the calibration sequence; According to the calibration sequence, each target calibration axis is calibrated in turn to obtain a target calibration angle corresponding to each target calibration axis.

11. The method for calibrating the posture of a print head according to any one of claims 1 to 9, characterized in that: After the step of calculating the target calibration angle of the target calibration axis based on the target calibration image, the method further comprises: If the absolute value of the target calibration angle is greater than a preset threshold, the posture of the target calibration axis is adjusted based on the target calibration angle.

12. An electronic device, characterized in that: The electronic device comprises: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program is configured to implement the steps of the method for calibrating the posture of the print head according to any one of claims 1 to 11.

13. A printing system, characterized in that: The printing system comprises a host computer and an inkjet printing device, wherein the host computer is in communication connection with the inkjet printing device; The host computer is used to obtain a target calibration angle of a target calibration axis based on the print head posture calibration method according to any one of claims 1 to 11, and send the target calibration angle to the inkjet printing device; The inkjet printing device is used to control the print head to print a target calibration pattern corresponding to a target calibration axis, and send a target calibration image including the target calibration pattern to a host computer, and adjust the posture of the target calibration axis based on the target calibration angle.

14. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method for calibrating the posture of a print head according to any one of claims 1 to 11 are implemented.

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