Method and equipment for pre-printing calibration of different spray heads and storage medium

Abstract

The invention discloses a method and equipment for pre-printing calibration of different spray heads and a storage medium. The method comprises the following steps: S1, obtaining a printer spray head distance and a color register calibration pattern; s2, setting resolutions matched with different nozzles in the calibration pattern; s3, the calibration pattern is imported into a printer, and the calibration pattern is printed; s4, performing visual identification on the printed calibration pattern, and respectively identifying a frame and a color block of the calibration pattern; s5, after the recognition result is obtained, the nozzle is calibrated through coarse adjustment scales on the right side and the lower portion of the calibration pattern; s6, after calibration, the calibration pattern is printed again; s7, the step S3 is repeated until the color blocks of the calibration pattern are completely overlapped in the square frame, the problems that in the prior art, the calibration difficulty is large, and lines and color spraying cannot be calibrated at the same time are solved, through the specific calibration pattern and visual recognition equipment, the nozzle distance and the color register condition can be accurately analyzed, the accurate offset can be obtained, and the purpose of fine calibration is achieved.

Description

Technical Field

[0001] The invention relates to the field of printers, and in particular to a method, a device and a storage medium for pre-printing calibration of different nozzles. Background Art

[0002] In terms of printer head calibration, traditional calibration methods have been widely used for a long time, but with the continuous development of printing technology, their drawbacks have become increasingly prominent. Traditional methods usually use specific calibration primitives for calibration operations. Specifically, they use calibration primitives composed of thick and thin vertical lines, and reference primitives composed of long and short lines. During the calibration process, the horizontal and vertical spacing presented by these primitives are measured and adjusted to achieve the calibration of the printhead.

[0003] However, this traditional calibration method has many problems. First, the calibration steps are extremely cumbersome. The operator needs to carefully compare the spacing between the various lines in the calibration graphics, and perform multiple measurements and adjustments according to specific standards and processes. For example, when measuring the horizontal spacing, it may be necessary to use tools such as a magnifying glass to accurately determine the distance between the thick vertical line and the thin vertical line, and then fine-tune the nozzle position according to the difference from the standard spacing; in terms of vertical spacing calibration, similar complex operations are also required for the reference graphics composed of long and short lines. The whole process is not only time-consuming and laborious, but also requires high skills and patience from the operator. The slightest carelessness may lead to inaccurate calibration.

[0004] Secondly, the traditional calibration method has great limitations in the resolution setting of the calibration chart. Usually, the resolution of the calibration chart is fixed to the base resolution of the printer. This means that the calibration process can only be performed at this specific resolution, and the calibration accuracy cannot be flexibly adjusted according to the actual printing requirements and the specific conditions of the printhead. For example, when a high-precision printing task is required and a higher accuracy of printhead calibration is required, the existing calibration chart resolution cannot meet this requirement, thereby limiting the accuracy of printhead calibration and affecting the final print quality.

[0005] Therefore, there is an urgent need for a method that can simplify the steps of printer nozzle spacing and color calibration, improve calibration efficiency and accuracy, and adapt to printing requirements of any resolution. Summary of the invention

[0006] In order to solve the above-mentioned technical problems, the present invention provides a method, a device and a storage medium for pre-printing calibration of different nozzles.

[0007] The technical solution of the present invention is achieved in this way:

[0008] A method for pre-printing calibration of different nozzles comprises the following steps:

[0009] S1, obtaining the printer nozzle spacing and color calibration pattern;

[0010] S2, setting the calibration pattern to match the resolution of different nozzles;

[0011] S3, importing the calibration pattern into the printer, and printing the calibration pattern;

[0012] S4, visually identifying the printed calibration pattern, and identifying the border and color blocks of the calibration pattern respectively;

[0013] S5, after obtaining the recognition result, calibrate the printhead through the coarse adjustment scales on the right and below the calibration pattern;

[0014] S6, after calibration, reprinting the calibration pattern;

[0015] S7, repeat step S3 until the color block with the calibration pattern coordinate (0, 0) is completely overlapped in the box.

[0016] Preferably, in step S1, the calibration pattern includes a plurality of groups of U-shaped boxes and square color blocks within the boxes, and the color blocks are exactly the same size as the small box in the middle of the U-shaped boxes.

[0017] Preferably, in step S1, there are scales on the right side and below the calibration pattern to facilitate coarse adjustment of the nozzle.

[0018] Preferably, in step S1, the calibration pattern format is PRN, and the resolution of the calibration pattern can be adjusted arbitrarily.

[0019] Preferably, in step S4, the printed calibration pattern is visually recognized. After the printer prints out the calibration pattern, the printed calibration pattern is image recognized by a visual recognition device of the printer.

[0020] Preferably, in step S5, the center position image of the calibration pattern, i.e., the pattern of coordinates (0, 0), is identified through image recognition, and the offset of the U-shaped box and the offset of the small square box of the square color block in the middle of the U-shaped box are determined according to the set scale.

[0021] Preferably, the visual recognition device includes a camera pre-installed at the printing outlet of the printer.

[0022] Preferably, the step S4 further comprises the following sub-steps:

[0023] S41, obtaining the calibration image after printing from step S3, inputting it into the printer control system, resetting the calibration pattern, and resetting the calibration pattern to the calibration pattern of the first printing result;

[0024] S42, according to the scale display, setting the calibration pattern of the first printing result to a coordinate system centered on the calibration pattern (0, 0);

[0025] S43, obtaining an offset according to the comparison calibration pattern;

[0026] Preferably, in step S5, the following sub-steps are also included:

[0027] S51, performing the first coarse adjustment according to the offset, adjusting in scale units;

[0028] S52, sending the roughly adjusted calibration pattern to the printer.

[0029] Preferably, in step S7, when the arrow on the scale does not point to the number 0, it is necessary to return to step S5 for adjustment, and when the arrow on the scale completely points to the number 0, the calibration is completed.

[0030] A printing device comprises at least one processor, at least one memory and computer program instructions stored in the memory, and the above method is implemented when the computer program instructions are executed by the processor.

[0031] A storage medium stores computer program instructions, wherein the method is implemented when the computer program instructions are executed by a processor.

[0032] The present invention solves the problems in the prior art of difficult calibration and inability to calibrate lines and colors at the same time. Through specific calibration patterns and visual recognition equipment, the nozzle spacing and color matching conditions can be accurately analyzed to obtain accurate offsets, and fine calibration can be achieved. The resolution can be adjusted arbitrarily, and different nozzle characteristics can be well matched to adapt to a variety of printers. By combining coarse adjustment with fine adjustment and adjusting according to scale units, repeated iterations are performed until the ideal calibration state is reached, thereby effectively improving the nozzle calibration accuracy, ensuring that the printer outputs high-quality images and documents, and improving printing quality and performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of a method for pre-printing calibration of different nozzles according to the present invention.

[0034] Figure 2 is a schematic diagram of a calibration pattern in an embodiment. DETAILED DESCRIPTION

[0035] In order to further explain the technical means and effects taken by the present invention to achieve the predetermined invention purpose, exemplary embodiments will be described in detail here, and examples thereof are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are only examples of methods and systems consistent with some aspects of the present application as detailed in the attached claims.

[0036] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0037] Example 1

[0038] like Figure 1 , 2 As shown, the present invention provides a method for pre-printing calibration of different nozzles, comprising the following steps:

[0039] S1, obtain the printer nozzle spacing and color calibration pattern; the calibration pattern includes multiple groups of U-shaped boxes and square color blocks in the boxes, and the color blocks are exactly the same size as the small box in the middle of the U-shaped box. On the right and below the calibration pattern, there are scales for coarse adjustment of the nozzle. The calibration pattern format is PRN, and the resolution of the calibration pattern can be adjusted arbitrarily; in addition to the basic digital logo and auxiliary marks, the coarse adjustment scale on the right and below the calibration pattern can increase the subdivision scale, and 5 subdivision scales are divided between each large scale, each subdivision scale represents a smaller nozzle adjustment amount, the large scale represents the nozzle moving 0.1 mm in a certain direction, and the subdivision scale can represent a movement of 0.02 mm, so that a more precise preliminary adjustment can be achieved during coarse adjustment.

[0040] S2. Set the calibration pattern to match the resolution of different printheads. By referring to the product manual of the printer or looking up the detailed parameters of the printheads in the printer settings software, determine the nominal resolution of each printhead (expressed in dots per inch, dpi). For example, the nominal resolution of a certain color printhead is 1200 dpi, and the nominal resolution of a certain black-and-white printhead is 600 dpi. For printheads that have been used for a long time, conduct a standard resolution test print. Print a test pattern consisting of equally spaced horizontal and vertical lines with a line width of 0.05 mm, and observe the clarity and integrity of the lines in the print result. If it is found that the lines are blurred, broken, etc., appropriately reduce the estimated actual resolution ability of the printhead. For example, a printhead originally estimated to be 1200 dpi may actually be set with a calibration pattern resolution of 1000 dpi after testing.

[0041] S3. Import the calibration pattern into the printer and print the calibration pattern. When the printer finishes printing the calibration pattern, the visual recognition device will be automatically activated to perform image capture and recognition operations on the just-printed calibration pattern.

[0042] S4. Conduct visual recognition on the printed calibration pattern, respectively recognize the border and color blocks of the calibration pattern, and use image recognition algorithms to analyze the linearity, continuity, and integrity of the overall shape of the border. Evaluate the linearity by calculating the deviation value between each side of the border and the ideal straight line. A deviation value less than 0.05 mm is considered good linearity. Judge the continuity by detecting whether there are breakpoints in the border lines. If there are no breakpoints, the continuity is good. Evaluate the integrity by observing whether the overall shape of the border conforms to the preset double-square shape. If the shape has no obvious deformation, the integrity is good.

[0043] Preferably, step S4 further includes the following sub-steps:

[0044] S41. Obtain the printed calibration image from step S3, input it into the printer control system, reset the calibration pattern to the calibration pattern of the first print result. After the printer finishes printing the calibration pattern, through the internal data transmission line connected to the printer, transfer the printed calibration image data from the printer's print output buffer to the printer control system.

[0045] S42. According to the scale display, set up a coordinate system with the calibration pattern of the first print result centered at the calibration pattern (0, 0). The control system stores it in a specific memory area and starts to execute the calibration pattern reset operation. First, clear any possible temporary data or settings related to the calibration pattern before to ensure that the system is in a brand-new state ready to process the calibration pattern of the first print result.

[0046] Then, the obtained post-printing calibration image data is marked as the calibration pattern of the first printing result, and the relevant system variables and pointers are updated to point to the newly marked calibration pattern data. In this way, all subsequent analyses and operations will be based on the calibration pattern of the first printing result. In order to more accurately represent the nozzle position and obtain the offset, the established coordinate system is further refined. Several subdivision scales are evenly divided between each large grid scale (such as 5 subdivision scales between each large grid), and each subdivision scale represents a smaller nozzle adjustment amount (such as each subdivision scale represents an adjustment amount of 0.02 mm for the nozzle to move in the corresponding direction).

[0047] Through the relevant setting functions in the printer control system, the information of these subdivided scales is accurately associated with the coordinate system, so that when the offset is obtained and adjustment operations are performed subsequently, the position change of the nozzle can be measured with finer scale units, thereby improving the accuracy of calibration.

[0048] S43, obtaining the offset according to the comparison calibration pattern, using an algorithm based on feature point matching (such as SIFT algorithm or SURF algorithm), taking the calibration pattern of the first printing result as a template, and performing pixel-by-pixel matching comparison with the calibration pattern actually printed. By calculating the position difference of the matching area, the offset of the U-shaped box and the square color block relative to the template (i.e., the calibration pattern of the first printing result) can also be effectively obtained;

[0049] For the offset calculation of the U-shaped box:

[0050] First, determine the coordinate representation of the four sides of the U-shaped box in the coordinate system. By identifying the positions of the corner points of the box in the coordinate system, determine the starting and ending coordinates of each side.

[0051] Then compare the coordinate changes of the four sides of the U-shaped box in the calibration patterns of different print results. Calculate the coordinate difference of each side relative to the corresponding side in the calibration pattern of the first print result, and obtain the offset in the x-axis and y-axis directions respectively. For example, the starting coordinates of a certain side in the calibration pattern of the first print result are (x1, y1), and the starting coordinates in the calibration pattern of the current print result are (x2, y2). Then the offset of the side in the x-axis direction is Δx = x2-x1, and the offset in the y-axis direction is Δy = y2-y1. Take the maximum absolute value of the offset of the four sides in each direction as the final offset of the U-shaped box in that direction.

[0052] Calculate the offset of the square color block in the small box in the middle of the U-shaped box:

[0053] Similarly, first determine the center coordinates of the square color block and the small box in the middle in the coordinate system. By identifying the geometric center positions of the color block and the small box, their coordinate representations in the coordinate system are obtained.

[0054] Then compare the coordinate changes of the center of the square color block relative to the center of the middle small square in different print result calibration patterns. Calculate the coordinate difference of the center of the square color block relative to the center of the middle small square in the x-axis and y-axis directions as the offset of the square color block in the direction. For example, the coordinates of the center of the square color block in the first print result calibration pattern are (x3, y3), and the coordinates in the current print result calibration pattern are (x4, y4), then the offset of the square color block in the x-axis direction is Δx = x4-x3, and the offset in the y-axis direction is Δy = y4-y3.

[0055] S44, obtaining the recognition result from step S7, inputting the recognition result into the printer control system, resetting the calibration pattern, and resetting the recognition result to the calibration pattern of the nth printing result;

[0056] S45, compare the calibration pattern of the nth printing result with the calibration patterns of the 1st to nth times, obtain the comparison of the offsets of the 1st to nth times and the scale, and obtain the accurate offset; in order to accurately compare the calibration pattern of the nth printing result with the calibration patterns of the 1st to nth times, a more complex and accurate image comparison algorithm is used. The advantages of multiple algorithms can be combined, such as first using an algorithm based on feature point matching (such as SIFT algorithm or SURF algorithm) to preliminarily locate the position change of key feature points, and then using a template matching algorithm to perform a more detailed matching comparison on the area around the key feature points;

[0057] For the offset of the circle:

[0058] Calculate the coordinate differences of the four sides of the U-shaped box in the calibration pattern of the nth printing result relative to the corresponding sides in the calibration patterns of the 1st to nth printing results, and obtain the offsets in the x-axis and y-axis directions in each comparison. For example, when comparing the calibration patterns of the nth printing results with the 1st printing results, the starting coordinates of a certain side in the 1st printing result are (x1, y1), and the starting coordinates in the nth printing result are (x2, y2). In this comparison, the offset of the side in the x-axis direction is Δx = x2-x1, and the offset in the y-axis direction is Δy = y2-y1.

[0059] Then, compare the offsets in these different comparisons with the scale. If each large scale represents an adjustment of 0.1 mm in the corresponding direction of the nozzle, and each subdivision between large scales represents an adjustment of 0.1 mm, then divide the calculated offset by the scale (such as dividing Δx by 0.1 or 0.02, depending on the actual corresponding scale unit) to get the offset value expressed in scale units.

[0060] Finally, these offset values ​​expressed in scale units are comprehensively considered, and the average value is taken or the weighted average value is calculated according to a certain weight (the weight can be set according to the importance or reliability of different comparisons) as the final accurate offset of the U-shaped box in this direction.

[0061] For the offset of the square color block in the small box in the middle of the U-shaped box:

[0062] Similarly, the coordinate differences of the centers of the square color blocks in the calibration pattern of the nth printing result relative to the corresponding centers in the calibration patterns of the first to nth printing results are calculated to obtain the offsets in the x-axis and y-axis directions in each comparison.

[0063] Next, these offsets are compared to the scale and converted to offset values ​​in scale units as described above.

[0064] Finally, these offset values ​​expressed in scale units are comprehensively considered, and the average value is taken or the weighted average value is calculated according to a certain weight as the final accurate offset of the square color block in this direction.

[0065] S5, after obtaining the recognition result, calibrate the printhead through the coarse adjustment scales on the right and below the calibration pattern;

[0066] Preferably, in step S5, the following sub-steps are also included:

[0067] S51, according to the offset, the first coarse adjustment is performed according to the scale unit; when the first coarse adjustment is performed according to the obtained offset, a coarse adjustment method is formulated to determine the size and direction of the offset. If the offset is large in a certain direction (such as exceeding a certain threshold, it can be set to half of each large grid scale, that is, 0.05 mm, if each large grid represents 0.1 mm adjustment), a larger adjustment method is preferred, that is, first adjust according to each large grid scale to quickly move the nozzle position to the correct direction.

[0068] If the offset is relatively small (less than the above threshold), you can start adjusting from the subdivision scale to get closer to the correct position more precisely and avoid over-adjustment. For example, if the offset of the square color block in the x-axis direction is 0.03 mm, and each large scale represents an adjustment of 0.1 mm, and each subdivision scale between large scales represents an adjustment of 0.02 mm, then first adjust 1 subdivision scale to the left to make the nozzle a small step closer to the correct position in the x-axis direction;

[0069] S52, sending the roughly adjusted calibration pattern to the printer.

[0070] S53, fine-tune the nozzle according to the offset obtained in step S57, and adjust the offset according to the scale unit compared with the scale. First, determine the size and direction of the accurate offset. If the offset is very small in a certain direction (such as less than one tenth of each large grid scale, that is, 0.01 mm, if each large grid represents 0.1 mm adjustment), then use the smallest scale unit for adjustment, that is, select the smallest adjustable unit from the subdivided scale (such as 10 subdivided scales between each large grid, each subdivided scale represents 0.01 mm adjustment), slowly approach the correct position, and avoid over-adjustment.

[0071] If the offset is relatively large (but less than the adjustment threshold during coarse adjustment, which can be set to half of each large scale, i.e. 0.05 mm), you can select a suitable scale unit combination for adjustment according to the size and direction of the offset. For example, if the offset of the square color block in the x-axis direction is 0.03 mm, each large scale represents an adjustment of 0.1 mm, and each subdivision between large scales represents an adjustment of 0.01 mm, you can first adjust 3 subdivisions to the left to make the nozzle a small step closer to the correct position in the x-axis direction, and then make further fine adjustments based on the new recognition results;

[0072] S54, sending the fine-tuned calibration pattern to the printer.

[0073] S6, after calibration, reprinting the calibration pattern;

[0074] S7, repeat step S3 until the color block with the calibration pattern coordinate (0, 0) is completely overlapped in the box.

[0075] Preferably, in step S4, the printed calibration pattern is visually recognized. After the printer prints out the calibration pattern, the printed calibration pattern is image recognized by a visual recognition device of the printer.

[0076] Preferably, in step S5, the center position image of the calibration pattern, i.e., the pattern of coordinates (0, 0), is identified through image recognition, and the offset of the U-shaped box and the offset of the small square box of the square color block in the middle of the U-shaped box are determined according to the set scale.

[0077] Preferably, the visual recognition device includes a camera pre-installed at the printing outlet of the printer.

[0078] Preferably, in step S7, when the arrow on the scale does not point to the number 0, it is necessary to return to step S5 for adjustment, and when the arrow on the scale completely points to the number 0, the calibration is completed.

[0079] A printing device comprises at least one processor, at least one memory and computer program instructions stored in the memory, and the above method is implemented when the computer program instructions are executed by the processor.

[0080] A storage medium stores computer program instructions, wherein the method is implemented when the computer program instructions are executed by a processor.

[0081] Example 2

[0082] In this embodiment, a method for pre-printing calibration of different print heads includes the following steps:

[0083] S1, select an industrial camera and install it in the working space of the printhead;

[0084] High-resolution industrial cameras, macro cameras and laser displacement sensors are selected as visual recognition equipment.

[0085] Install a high-resolution industrial camera at a suitable position above the nozzle to ensure that the overall appearance and structure of the nozzle can be clearly captured. The distance can be determined according to the size of the nozzle and the camera's field of view, generally maintained at around 10-30 cm, and the installation must be stable to avoid shaking.

[0086] The macro camera is installed close to the inkjet nozzle and focuses on the details of the inkjet nozzle to clearly capture the formation and injection of ink droplets. The angle and distance must be precisely adjusted during installation to ensure the best imaging effect. The distance from the inkjet nozzle is usually within 1-5 cm.

[0087] The laser displacement sensor is installed on the side of the print head to monitor the displacement changes of the print head during operation. The installation position must ensure that the relevant displacement data of the print head can be accurately measured and it must be firmly fixed to prevent displacement during the operation of the printer.

[0088] Set the resolution to 2560×1440 pixels or higher to obtain a clear image of the entire printhead.

[0089] Adjust the focal length so that the entire nozzle is completely within the clear imaging range. This can be achieved through the camera's built-in focus function or manual adjustment of the lens.

[0090] Set the contrast to 50%-70%, the brightness to 60%-80%, and fine-tune the color balance according to the actual ambient light conditions to ensure that the image colors are true and the details are clearly visible.

[0091] For macro camera:

[0092] Set the resolution to 5000 x 3000 pixels or higher to accurately observe the fine details of ink droplets.

[0093] Adjust the focal length to be able to focus clearly within the diameter of the inkjet nozzle. Professional macro focusing tools can be used for precise adjustment.

[0094] Similarly, set the contrast, brightness and other parameters, such as contrast to 60%-80% and brightness to 70%-90%, to improve image quality.

[0095] For laser displacement sensors:

[0096] According to the possible displacement range of the nozzle, the measurement range is set to about ±0.5 mm.

[0097] Set the accuracy to 0.01 mm or better to accurately measure small displacement changes of the printhead.

[0098] Set the sampling frequency to 100 times per second or higher to ensure that the displacement information of the printhead can be captured in time.

[0099] S2, obtaining nozzle parameters through visual recognition;

[0100] Use a high-resolution industrial camera to capture the printhead image, making sure the printhead is completely in the center of the image and clearly visible.

[0101] Import the captured image into professional image analysis software (such as ImageJ, etc.), use edge detection algorithm (such as Canny edge detection algorithm) to identify the boundary contour of the nozzle, and accurately locate the edge position of the nozzle.

[0102] In the image coordinate system, measure the distance between each key point on the nozzle profile, such as the distance between the key endpoints in the length, width, and height directions of the nozzle. Combined with the known image scale (determined by photographing a standard-sized object in advance and measuring its size in the image, such as photographing a square object with a side length of 10 mm, measuring its pixel size in the image, and then calculating the image scale), calculate the overall size parameters such as the actual length, width, and height of the nozzle.

[0103] The printhead image taken by the high-resolution industrial camera is imported into the image analysis software again. By identifying the color, shape, texture and other features of the different parts inside the printhead, the positions of key components such as the inkjet port, ink line interface, heating element (for thermal inkjet printhead) or piezoelectric ceramic element (for piezoelectric inkjet printhead) are distinguished.

[0104] Using image segmentation technology, the printhead image is segmented into different areas, each of which corresponds to a component or a group of related components. By analyzing the positions and relationships of these areas, the layout of each component inside the printhead is determined, and the relative position information of each component is recorded in detail.

[0105] The macro camera is started to continuously capture a continuous image sequence of ink droplet formation and ejection from the inkjet nozzle. The shooting speed is set to at least 30 frames per second to ensure that the dynamic process of the ink droplet can be fully captured.

[0106] The captured image sequence is imported into professional image processing software (such as Adobe Photoshop, etc.), and the outline of a single ink droplet is identified using particle image velocimetry (PIV) or related image processing algorithms.

[0107] The actual diameter of each ink droplet is calculated based on the image scale (determined by photographing a tiny object of known size and measuring its size in the image in advance, such as photographing a circular object with a diameter of 0.1 mm and measuring its pixel size in the image to calculate the image scale). A large number of ink droplets are measured and statistically analyzed to obtain the ink droplet size distribution range that the printhead can produce, including parameters such as the minimum ink droplet diameter, the maximum ink droplet diameter, and the average ink droplet diameter.

[0108] Continue to use the ink droplet ejection image sequence taken by the macro camera, set a fixed observation area in the image, which should cover the main inkjet area near the inkjet outlet of the nozzle. The area can be determined according to the size and distribution of the inkjet outlet of the nozzle, which is generally a few square centimeters.

[0109] Count the number of ink droplets that appear in the area within a certain time interval (such as 1 second) as the approximate value of the inkjet frequency. To improve the measurement accuracy, repeat the above operation at least 5 times, changing a different observation area each time, and then take the average value as the final inkjet frequency parameter. At the same time, combined with the printer's working mode (such as draft mode, standard mode, high-quality mode, etc.), analyze the changes in inkjet frequency in different modes, and record the inkjet frequency values ​​in different modes in detail.

[0110] From the ink droplet ejection image captured by the macro camera, the starting point (i.e., the ink jet position) and the end point (i.e., the point where the ink droplet lands on the paper or simulated medium) of the ink droplet are determined, and can be marked using the marking function in the image analysis software.

[0111] Using trigonometric functions, calculate the angle between the ink droplet's ejection direction and the nozzle plane and the offset angle relative to the horizontal or vertical direction. Perform statistical analysis on the ejection directions and angles of a large number of ink droplets (at least 100) and calculate the average ejection direction and angle, as well as the standard deviation of the angle and other statistics, so as to understand the ejection law of the ink droplets under normal working conditions of the nozzle and record the relevant data in detail.

[0112] The laser displacement sensor monitors the displacement changes of the nozzle in real time during the operation of the printer. The sensor continuously sends and receives laser signals, and measures the displacement of the nozzle relative to the initial position based on the principle of time difference or phase difference of reflected light.

[0113] The displacement data of the nozzle is recorded at regular time intervals (such as 0.1 seconds), and is continuously monitored during a complete printing cycle of the printer. The collected data is stored in a special data file for subsequent analysis.

[0114] Combining the nozzle displacement monitoring data and time information, the movement speed of the nozzle at different stages (such as the start of printing, during printing, and at the end of printing) is calculated by deriving the displacement data or using a differential algorithm.

[0115] The calculated nozzle speed data are arranged in chronological order to form a nozzle speed change curve, the fluctuation of the curve is analyzed, and information such as the nozzle speed value at different stages and the amplitude of speed fluctuation is recorded in detail.

[0116] S3, build a virtual printing environment;

[0117] Choose professional virtual printing software, such as FinePrint, PDFCreator, etc. These software should have powerful simulation functions and be able to accurately simulate the actual printing process based on the input nozzle parameters and other related printing settings.

[0118] Make sure the selected software is compatible with the operating system you are using. For example, if you are using Windows, choose a version that supports Windows and can easily import nozzle parameters and other necessary printing settings information.

[0119] Accurately input various parameters of the printhead obtained through the visual recognition device into the virtual printing software. Specifically including:

[0120] The overall size parameters (length, width, height) of the nozzle, component layout information and other appearance and structural parameters.

[0121] Inkjet characteristic parameters such as ink drop size distribution range, inkjet frequency, inkjet direction and angle.

[0122] Nozzle displacement monitoring data, nozzle speed change curve and other motion characteristic parameters.

[0123] During the input process, format settings and data filling are performed according to the software requirements to ensure that the software can correctly identify and apply these parameters for virtual printing simulation.

[0124] Determine the output format of the virtual print result. You can choose to save the output result in a common image format, such as PNG, JPEG, etc. Considering the image quality preservation and the compatibility of the subsequent analysis software with this format, it is generally recommended to choose the PNG format.

[0125] Set the resolution of the output image according to the resolution parameters of the printhead (such as the actual print resolution that the printhead can achieve obtained through the visual recognition device) to match the actual print accuracy that the printhead can achieve. For example, if the resolution of the printhead is 1200dpi, the resolution of the virtual print output image can also be set to 1200dpi, so as to more intuitively compare the virtual print result with the actual print result.

[0126] S4, performing virtual printing simulation;

[0127] In the virtual printing software, a virtual printing task is created according to the set nozzle parameters, printing environment parameters, output format, etc.

[0128] Select the content to be printed, which can be a simple test pattern, such as a pattern composed of lines, geometric figures, color blocks, etc., or an actual document or image file. If you choose a test pattern, you can design it yourself or select it from the test pattern library provided by the software to ensure that the selected pattern can fully reflect the performance of the printhead in different printing situations.

[0129] Specifying the number of copies, setting the print orientation (such as portrait or landscape), and other general print task settings are similar to the actual print task settings.

[0130] Start the virtual printing simulation task and let the virtual printing software simulate the actual printing process and generate virtual printing results according to the input parameters and settings. During the simulation process, the software will simulate the actual printing process such as ink jetting, paper absorption, color mixing, etc. according to the parameters such as the ink jetting method of the nozzle, ink drop size distribution, color channel configuration, etc.

[0131] Observe the progress of the virtual printing simulation. The virtual printing software usually provides a progress bar or other prompt information to show the completion progress of the simulation task. Wait for the simulation task to complete and obtain the generated virtual printing results.

[0132] S5, virtual printing result analysis

[0133] Open the generated virtual print results in image form and use professional image viewing software (such as Adobe Photoshop, etc.) for visual analysis.

[0134] Observe the overall clarity of the print result and check for blurriness, jagged edges, etc. If the virtual print result is blurry, it may indicate that the resolution of the printhead is not set properly or the ink drop size is not well controlled; if jagged edges appear, it may be caused by insufficient inkjet accuracy of the printhead or uneven speed at which the paper absorbs ink.

[0135] For color printing results, analyze the color accuracy and naturalness of color transitions. Check whether the color matches the original image or expected color, and whether there is color cast or fading. Observe whether the color transition is smooth, such as whether there is a clear discontinuity or jump in the transition area from red to orange, from blue to green, etc. These problems may be related to factors such as the color channel configuration of the color nozzle, the ink drop size distribution, and the mixing ratio of the ink.

[0136] Analyze the integrity of graphics and text in the print results to see if there are any missing or deformed parts. If there are missing parts in graphics or text, it may be due to insufficient ink jetting from the printhead or inaccurate relative positioning of the printhead and paper; if there is deformation, it may be due to uneven movement of the printhead or movement of the paper when it is opened.

[0137] Use professional image analysis software (such as ImageJ, etc.) to perform data quantitative analysis on the virtual printing results.

[0138] Measure the width and length of the lines in the print result, compare them with the line size of the original design, and calculate the deviation rate. A large deviation rate may mean that the inkjet accuracy of the printhead is not enough or the movement speed of the printhead is not well controlled.

[0139] For color printing results, analyze the quantitative indicators of color. For example, in the RGB or CMYK color space, calculate the color value of each pixel and compare it with the color value of the original image to calculate the color difference (such as ΔE value). The larger the ΔE value, the greater the color deviation, which may be caused by factors such as the color channel configuration of the color nozzle, the ink drop size distribution, and the mixing ratio of the ink.

[0140] Analyze the distribution of ink droplets in the print results, and use the relevant functions of the software to count the number, size, and distribution density of ink droplets. Compare these parameters with the ink drop size distribution range of the printhead to see if there are ink droplets that are too large or too small, too densely distributed or sparsely distributed. These situations may affect the print quality, such as causing ink accumulation, uneven color, and other problems.

[0141] S6, calibrate the nozzle

[0142] Based on the visual analysis and data quantitative analysis results of the virtual printing results, determine the direction and magnitude of the printhead calibration. For example, if the visual analysis finds that the print result is blurred in the vertical direction, and the data quantitative analysis shows that the printhead has a large deviation in the inkjet accuracy in the vertical direction, then the printhead needs to be calibrated in the vertical direction, and the calibration magnitude can be determined based on the magnitude of the deviation. If the deviation is small, fine-tuning can be performed; if the deviation is large, a larger adjustment may be required.

[0143] For color printing results, if the color deviation is large, such as the ΔE value exceeds the acceptable range (generally it can be set according to the print quality requirements, such as a ΔE value greater than 5 can be considered a large color deviation), then it is necessary to calibrate the color channel of the color nozzle and adjust the inkjet volume, mixing ratio and other parameters of the color channel to improve color accuracy and the naturalness of color transitions.

[0144] The actual calibration operation of the printhead is performed through the printer's setup software or a special printhead calibration tool. When performing the calibration operation, adjustments must be made in accordance with the determined calibration direction and amplitude. For example, if the printhead needs to be fine-tuned in the vertical direction, the fine-tuning function in the setup software can be used to adjust it according to a certain scale unit (such as each grid represents 0.1 mm movement of the printhead in the vertical direction); if the color channel of the color printhead needs to be adjusted, the corresponding color channel adjustment option can be found in the setup software, and the inkjet volume, mixing ratio, etc. can be adjusted according to the analysis results.

[0145] During the calibration process, pay close attention to the printer's status and feedback information. Some printers will provide real-time status display during calibration, such as changes in parameters such as nozzle pressure, ink jet volume, temperature, etc. By observing these feedback information, you can promptly discover possible problems, such as nozzle blockage, ink supply system failure, etc., and take appropriate measures to deal with them.

[0146] After completing the printhead calibration operation, perform virtual printing simulation again and regenerate the virtual printing result according to the previous settings. Then, perform the same visual analysis and data quantitative analysis on the new virtual printing result to check whether the calibration effect meets expectations. If the calibration effect is not ideal, such as obvious blurring, color deviation and other problems, it is necessary to re-analyze the calibration results, adjust the calibration strategy, and continue the calibration operation until a satisfactory calibration effect is obtained.

[0147] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for pre-printing calibration of different nozzles, characterized in that: The steps include: S1, obtaining the printer nozzle spacing and color calibration pattern; S2, setting the calibration pattern to match the resolution of different nozzles; S3, importing the calibration pattern into the printer, and printing the calibration pattern; S4, visually identifying the printed calibration pattern, and identifying the border and color blocks of the calibration pattern respectively; S5, after obtaining the recognition result, calibrate the printhead through the coarse adjustment scales on the right and below the calibration pattern; S6, after calibration, reprinting the calibration pattern; S7, repeat step S3 until the color block with the calibration pattern coordinate (0, 0) is completely overlapped in the box.

2. A method for pre-printing calibration of different print heads according to claim 1, characterized in that: In step S1, the calibration pattern includes a plurality of groups of U-shaped boxes and square color blocks in the boxes, and the color blocks are exactly the same size as the small box in the middle of the U-shaped boxes.

3. A method for pre-printing calibration of different print heads according to claim 1, characterized in that: In step S1, there are scales on the right and below the calibration pattern to facilitate coarse adjustment of the nozzle.

4. A method for pre-printing calibration of different print heads according to claim 1, characterized in that: In step S1, the calibration pattern format is PRN, and the resolution of the calibration pattern can be adjusted arbitrarily.

5. The method for pre-printing calibration of different nozzles according to claim 1, characterized in that: In step S4, the printed calibration pattern is visually recognized. After the printer prints the calibration pattern, the printed calibration pattern is image recognized by a visual recognition device of the printer.

6. A method for pre-printing calibration of different print heads according to claim 1, characterized in that: In step S5, the center position image of the calibration pattern, that is, the pattern of coordinates (0, 0), is identified through image recognition, and the offset of the U-shaped box and the offset of the small box in the middle of the U-shaped box are determined according to the set scale.

7. A method for pre-printing calibration of different print heads according to claim 1, characterized in that: The step S4 also includes the following sub-steps: S41, obtaining the calibration image after printing from step S3, inputting it into the printer control system, resetting the calibration pattern, and resetting the calibration pattern to the calibration pattern of the first printing result; S42, according to the scale display, setting the calibration pattern of the first printing result to a coordinate system centered on the calibration pattern (0, 0); S43, obtaining an offset according to the comparison calibration pattern.

8. The method for pre-printing calibration of different nozzles according to claim 1, characterized in that: In the step S5, the following sub-steps are also included: S51, performing the first coarse adjustment according to the offset, adjusting in scale units; S52, sending the roughly adjusted calibration pattern to the printer.

9. A printing device, comprising at least one processor, at least one memory and computer program instructions stored in the memory, wherein when the computer program instructions are executed by the processor, the method according to any one of claims 1 to 8 is implemented.

10. A storage medium having computer program instructions stored thereon, characterized in that: When the computer program instructions are executed by a processor, the method described in any one of claims 1 to 8 is implemented.

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