Vision-based multi-ink-box calibration method

Abstract

The invention belongs to the field of clothing and footwear printing, and relates to a vision-based multi-ink-box calibration method. The multiple ink boxes are mainly used for calibration of the multiple ink boxes, firstly, a multi-ink-box printer executes a printing command to print a pattern needed by calibration, then the straight lines printed by the multiple ink boxes are shot and recognized through an industrial camera, and the installation position relation among the multiple ink boxes is calculated through printed data. And the ink outlet time of different ink boxes and the overlapping amount of the x direction and the y direction are adjusted in a subsequent control system according to the position relation. According to the invention, the calibration precision and the automation degree of the multi-cartridge printer are improved, so that the printing efficiency and quality are improved.

Description

Technical Field

[0001] The invention relates to the field of digital printing, and in particular to a multi-ink cartridge calibration method. Background Art

[0002] At present, most printers use a single ink cartridge. When a single ink cartridge is converted into a multi-ink cartridge, the size of the ink cartridge is much larger than the printing area during installation. If it is arranged in a straight line, there will be a large blank area where data cannot be printed. If the height is increased to make the printing area parallel, the ink cartridge will move too fast during printing, which will cause the final position of the ink drop to be inaccurate, reducing the accuracy. The most suitable height is within 2mm. Then the print data also needs to be printed in chronological order from the control end.

[0003] Before calibration, a multi-cartridge printer may have duplicate printing areas or the printing time between different cartridges may not be well controlled. Currently, most multi-cartridge calibrations are done manually and require manual adjustment. Machine vision is now used to calibrate multi-cartridges, which optimizes accuracy and efficiency compared to manual calibration. The distance between the cartridges after installation can now be directly measured by vision to adjust the output of later printing data. Summary of the invention

[0004] In order to optimize the calibration process of a multi-ink cartridge printer, the object of the present invention is to provide an automatic multi-ink cartridge calibration method, and the technical solution adopted is as follows:

[0005] The method is applicable to a scenario where a printer uses multiple ink cartridge pairs for printing at the same time, and the method comprises:

[0006] Printing module: The control terminal sends the printing command, and the printer executes the printing command after receiving it, and the ink cartridge prints.

[0007] Image extraction module: Use industrial cameras to capture, store and transmit printed images

[0008] Image analysis module: processes the captured image and extracts the feature area. Calculates the distance between each ink cartridge in the x and y directions based on the straight lines printed by each ink cartridge.

[0009] The equipment of the method includes: an industrial camera, a printing workbench, a first ink cartridge, a second ink cartridge, a third ink cartridge, and a fourth ink cartridge, such as Figure 2 shown.

[0010] The first ink cartridge, the second ink cartridge, the third ink cartridge, and the fourth ink cartridge are arranged horizontally and alternately on the print head, such as Figure 3 shown.

[0011] The printing instruction for calibrating the ink cartridge is that the first ink cartridge, the second ink cartridge, the third ink cartridge, and the fourth ink cartridge simultaneously print a straight line parallel to the x direction, such as Figure 4 shown.

[0012] The industrial camera is used to shoot the printing area on the printing table, and the image is transmitted to the image processing end through the USB data cable and the network cable. The shooting angle of the industrial camera is perpendicular to the plane of the printing table.

[0013] The image processing includes:

[0014] Use Gaussian filtering to denoise the image. The expression of this process is as follows:

[0015]

[0016] Among them, f(x,y) is the Gaussian distribution function, σ is the standard deviation, and the standard deviation determines the width and smoothness of the Gaussian function.

[0017] Use threshold segmentation to extract the printed straight lines parallel to the x direction; calculate the difference between the four straight lines printed by the four ink cartridges in the x and y directions respectively, and the threshold segmentation process is as follows:

[0018] (1) Calculate histogram: Perform grayscale histogram statistics on the image to obtain the number of pixels at each grayscale level.

[0019]

[0020] Among them, pi is the probability of the i-th gray level, ni is the number of pixels at that gray level, and N is the total number of pixels.

[0021] (2) Initialization: Initialize the inter-class variance to 0, and initialize the total average grayscale and total number of pixels.

[0022]

[0023] Where L is the number of gray levels.

[0024] (3) Traversing thresholds: For each possible threshold t, perform the following calculations:

[0025]

[0026] (4) Select the maximum variance: Select among all thresholds such that The maximum threshold t optimal .

[0027]

[0028] The optimal threshold t obtained by OTSU algorithmoptimal , through this threshold, the image can be binarized, making the target in the image more prominent.

[0029] The pixel coordinates of the pixels at both ends of each straight line are extracted from the processed image to obtain the pixel distance between the straight lines, which is then converted into the real distance in world coordinates.

[0030] The difference in the y direction is the distance between each printing interval after the ink cartridge is installed; the difference in the x direction is the overlap of the printing intervals when the ink cartridge is installed.

[0031] The coordinate difference obtained after image processing is transmitted to the timing control system. The timing control system controls and allocates the printing data. The printing time of each ink cartridge is adjusted by the difference in the y direction. The overlapping printing intervals are adjusted by the difference in the x direction to prevent repeated printing or blank printing intervals.

[0032] During the printing process, the ink cartridge will move back and forth, so the printing order and printing time need to be adjusted in both directions. During the round trip process, a print command is sent at the same position in the y direction but different positions in the x direction, and the printing time of multiple ink cartridges is adjusted by the distance difference between the two prints. The two print positions and distance difference are as follows: Figure 5 Shown

[0033] The embodiments of the present invention have at least the following beneficial effects:

[0034] The present invention firstly allows the multi-cartridge printer to execute a print command, identifies the straight lines printed by the multiple ink cartridges through an industrial camera, and calculates the installation position relationship between the multiple ink cartridges using the printed data. Then, the ink output time of different ink cartridges is adjusted in the subsequent control system according to the position relationship. The present invention improves the calibration accuracy and automation degree of the multi-cartridge printer, thereby improving production efficiency and quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 It is a flow chart of a calibration method for a multi-ink cartridge printer disclosed in the present invention;

[0037] Figure 2 It is a schematic diagram of an embodiment of the calibration method device disclosed in the present invention;

[0038] Figure 3It is a schematic diagram of the installation of multiple ink cartridges disclosed in the present invention;

[0039] Figure 4 The present invention is a schematic diagram of a multi-ink cartridge position calibration process of the calibration method disclosed in the present invention.

[0040] Figure 5 It is a schematic diagram of the round-trip calibration process of the calibration method disclosed in the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with preferred embodiments. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0042] The accompanying drawings are schematic diagrams of embodiments of the present invention. It should be noted that the drawings are only for illustration and are not drawn in accordance with the conditions of equal proportions, and should not be used as a limitation on the actual scope of protection claimed in the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs.

[0043] The specific scheme of the visual identification system for spinning quality provided by the present invention is described in detail below with reference to the accompanying drawings.

[0044] Example:

[0045] The specific scenarios targeted by the embodiments of the present invention are:

[0046] See also Figure 1 , which shows a schematic flow chart of a calibration method for a multi-ink cartridge printer provided by an embodiment of the present invention, the method comprising:

[0047] Printing module: The control terminal sends the printing instruction, and the printer executes the printing command after receiving it, and the ink cartridge prints.

[0048] Image extraction module: Use industrial cameras to capture, store and transmit printed images.

[0049] Image analysis module: pre-process the captured image and extract the feature area. Calculate the distance between the printed lines in the x and y directions.

[0050] See also Figure 2 The equipment provided in the example of this application includes: an industrial camera, a printing workbench, a first ink cartridge, a second ink cartridge, a third ink cartridge, and a fourth ink cartridge.

[0051] In this example, four ink cartridges are installed in a staggered arrangement. For details on how to install them, please refer to Figure 3

[0052] Printing module: First, the control terminal issues a printing command, which is for the first, second, third, and fourth ink cartridges to print a straight line parallel to the x direction at the same time. The length of the straight line is the length of the inkjet range of the ink cartridge, which is 25.4mm. Please refer to the printed image Figure 4 .

[0053] In addition, the width of the printed straight line is the width of one pixel in the later image processing, which is convenient for extracting the endpoint coordinates.

[0054] The printing area on the printing table is photographed by an industrial camera, and the photographed image is transmitted to the image processing end via a USB data cable and a network cable. The shooting angle of the industrial camera is perpendicular to the plane of the printing table.

[0055] The acquired image must be preprocessed at the control end to extract the required feature area. The preprocessing of the image includes: using Gaussian filtering to remove

[0056] Noise processing; use threshold segmentation to extract the printed straight lines parallel to the x direction.

[0057] After image preprocessing, the pixel coordinate values ​​of the two end points of the four straight lines are extracted respectively, and the coordinate value differences of these pixel points in the x direction and in the y direction are calculated in turn.

[0058] The difference in the x direction is the distance between each printing section after the ink cartridge is installed; the difference in the y direction is the overlap of the printing sections when the ink cartridge is installed. The coordinate difference is transmitted to the timing control system. The timing control system controls and allocates the printing data. The printing time of each ink cartridge is adjusted by the difference in the x direction. The overlapping printing sections are adjusted by the difference in the y direction to prevent repeated printing.

[0059] The above content is an explanation of the preferred embodiments of the present invention, which can help those skilled in the art to more fully understand the technical solution of the present invention. However, these embodiments are merely illustrative, and it cannot be determined that the specific implementation methods of the present invention are limited to the description of these embodiments. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions and transformations can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A multi-ink cartridge calibration method based on vision, characterized in that: The method is applicable to a scenario where a printer uses multiple ink cartridge pairs for printing at the same time, and the method comprises: Printing module: The control terminal sends the printing command, and the printer executes the printing command after receiving it, and the ink cartridge prints. Image extraction module: Use industrial cameras to capture, store and transmit printed images Image analysis module: processes the captured image and extracts the feature area. Calculates the distance between each ink cartridge in the x and y directions based on the straight lines printed by each ink cartridge.

2. A vision-based multi-ink cartridge calibration method, characterized in that: The equipment of the method comprises: an industrial camera, a printing workbench, a first ink cartridge, a second ink cartridge, a third ink cartridge, and a fourth ink cartridge.

3. The visual-based multi-ink cartridge calibration method as claimed in claim 2, characterized in that The first ink cartridge, the second ink cartridge, the third ink cartridge, and the fourth ink cartridge are arranged laterally and alternately on the print head.

4. The visual-based multi-ink cartridge calibration method as claimed in claim 1, characterized in that The printing instruction for calibrating the ink cartridge is that the first ink cartridge, the second ink cartridge, the third ink cartridge, and the fourth ink cartridge simultaneously print a straight line parallel to the x direction. The length of the straight line is the length of the inkjettable range of the ink cartridge.

5. The vision-based multi-ink cartridge calibration method as claimed in claim 1, characterized in that The industrial camera is used to shoot the printing area on the printing table, and the image is transmitted to the image processing end via a USB data cable and a network cable. The shooting angle of the industrial camera is perpendicular to the plane of the printing table.

6. The vision-based multi-ink cartridge calibration method according to claim 1, characterized in that: The image processing includes: Use Gaussian filtering to denoise the image; Use threshold segmentation to extract the printed straight lines parallel to the x direction; The differences in the x and y directions between the four straight lines printed by the four ink cartridges are obtained by calculation.

7. The vision-based multi-ink cartridge calibration method as claimed in claim 1, characterized in that It is necessary to extract the pixel coordinates of the pixel points at both ends of each straight line, obtain the pixel distance between the straight lines, and then convert the real distance in world coordinates.

8. The visual-based multi-ink cartridge calibration method as claimed in claim 7, characterized in that The difference in the y direction is the distance between each printing interval after the ink cartridge is installed; the difference in the x direction is the overlap of the printing intervals when the ink cartridge is installed.

9. The visual-based multi-ink cartridge calibration method as claimed in claim 8, characterized in that The coordinate difference obtained after image processing is transmitted to the timing control system. The timing control system controls and allocates the printing data. Among them, the printing order and printing time of different ink cartridges in the multi-ink cartridge are adjusted by the difference in the y direction. The overlapping printing intervals are adjusted by the difference in the x direction to prevent repeated printing or blank printing intervals.

10. The vision-based multi-ink cartridge calibration method as claimed in claim 1, characterized in that During the printing process, the ink cartridge will move back and forth, so the printing order and printing time need to be adjusted in both directions. During the round trip process, a print command is sent at the same position in the y direction but different positions in the x direction, and the printing time of multiple ink cartridges is adjusted by the difference in the distance between the two prints.

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