A method for controlling ink drop charging for two-dimensional code printing

Abstract

This invention relates to a method for controlling ink droplet charging in QR code printing, characterized by the following steps: S1. After acquiring the original QR code image, the original QR code image is divided into N columns of blocks in a column-by-column manner; S2. Each column of blocks is scanned and analyzed sequentially to determine the position and coverage of the black and white areas on each column of blocks; S3. The charging spacing corresponding to each black block and the charging capacity corresponding to each ink droplet within the block are calculated; S4. During printing, the corresponding ink droplet is selected according to the charging spacing of each black area, and the selected ink droplet is charged to the required capacity to complete the printing. This method can effectively reduce the influence of Coulomb forces on charged ink droplets during flight, improve the situation where charged ink droplets deviate from their correct flight trajectory, make the printed QR code less prone to deformation, and improve the printing quality.

Description

Technical Field

[0001] This invention relates to the field of continuous inkjet printing technology, and more specifically to a method for controlling ink droplet charging in QR code printing. Background Technology

[0002] CIJ is an abbreviation for continuous ink jet, also known as non-contact printing.

[0003] A continuous inkjet system ejects ink continuously from a single nozzle under pressure. After being oscillated by a crystal, the ink breaks into continuous droplets. Some of these droplets are charged, and the charged droplets are deflected by a high-voltage electric field before being ejected. The uncharged droplets flow back in a straight line to the droplet collection head and return to the circulating ink path. The charged droplets are deflected and ejected onto the surface of a moving object to scan and form characters or graphics.

[0004] Continuous inkjet printing technology is generally used in the packaging market where imaging requirements are relatively low but printing speed is very high. For example, continuous inkjet printing is the best solution for numbering and marking on packaging for food, beverages, electronic components, and pharmaceuticals.

[0005] Continuous inkjet printing technology is now very mature for printing characters and barcodes, and it can balance print quality and printing speed.

[0006] Because the ejected ink droplets are charged, each ejected ink droplet carries an electrical charge.

[0007] When printing QR codes, because the black area of ​​the QR code is relatively large, the print head ejects a large number of ink droplets. The number of ink droplets that need to be charged is also large, and the charged ink droplets are densely arranged. During the flight, the charged ink droplets may interfere with each other due to the Coulomb force, causing some ink droplets to deviate from their ejection trajectory to a certain extent, resulting in a deformed QR code.

[0008] This is also the reason why printing distortion inevitably occurs when using CIJ to print QR codes. The above-mentioned technical problems need to be overcome. Summary of the Invention

[0009] Based on the above description, the present invention provides a method for controlling ink droplet charging in QR code printing, which can improve the problem of deformation during QR code printing and improve the quality of QR code printing.

[0010] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0011] A method for controlling ink droplet charging in QR code printing includes the following steps:

[0012] S1. After obtaining the original QR code image, divide the original QR code image into N columns of image blocks in a column-by-column manner;

[0013] S2. Scan and analyze each column of blocks sequentially to determine the position and coverage of the black and white areas on each column of blocks;

[0014] S3. Calculate the charging spacing corresponding to each black block and the charging power corresponding to each ink droplet within the block.

[0015] S4. During printing, select the corresponding ink droplets according to the charging spacing of each black area, charge the selected ink droplets to the required power, and complete the printing.

[0016] As a preferred solution: after obtaining the original QR code image in step S1, a Cartesian coordinate system is established, the original QR code image is placed in the coordinate system, and then the original QR code image is divided into N columns of image blocks, so that the coordinate range of the area where each image block is located can be obtained.

[0017] As a preferred solution: In step S2, each pixel in the image block is first scanned to obtain the color value of each pixel. Then, white pixels and black pixels are distinguished according to the color value, so as to determine the coverage range of the white and black areas in each image block, i.e., the coordinate range.

[0018] As a preferred approach: In step S3, for each black area, first calculate the charging power corresponding to the minimum ordinate point A and the maximum ordinate point B within that black area, where the charging power for point A is Qa and the charging power for point B is Qb. If the number of vertical pixels between points A and B is P, then the charging power difference between adjacent pixels in the vertical direction can be considered to be (Qa-Qb) / P. Based on this, the charging power corresponding to each pixel between points A and B can be calculated. Then, using the Coulomb formula F=k*q1*q2 / d², the charging power of the ink droplet at point A and the charging power of other pixels below point A can be calculated. The Coulomb force values ​​between ink droplets at each pixel are used to obtain the Coulomb force array within the black area. Repeating this process yields the Coulomb force arrays for all black areas within each column of the image. The Coulomb force values ​​in each black area's array are then compared one by one with the preset Coulomb force reference value Fc to find the Coulomb force value Fz that is closest to Fc and smaller than Fc for each black area. The two pixels corresponding to the Coulomb force value Fz are then identified, and the distance between the ink droplets corresponding to these two pixels, i.e., the charging distance, can be determined, thus enabling the determination of the ink droplet charging distance for each black area.

[0019] As a preferred option: after determining the charging spacing of each black area, in step S4, some ink droplets corresponding to the black area with the smallest charging spacing are randomly inserted into the ink droplet groups of each black area with a larger charging spacing, and the ink droplets are only inserted into the positions of the ink droplet groups with lower charging power.

[0020] Compared with the prior art, the technical solution of this application has the following beneficial technical effects:

[0021] This application first segments, scans, and parses the QR code to be printed to obtain the coverage area of ​​the black and white areas of each column of the QR code. Then, based on the coverage area, it calculates the charging distance and charging power of the ink droplets in each black area. During printing, the corresponding ink droplets are selected according to the charging distance of each black area, and the selected ink droplets are charged to the required power to complete the printing. This method can effectively reduce the influence of Coulomb forces on the charged ink droplets during flight, improve the situation where charged ink droplets deviate from their correct flight trajectory, make the printed QR code less prone to deformation, and improve the printing quality. Attached Figure Description

[0022] Figure 1 A diagram illustrating the segmentation of a QR code column by column;

[0023] Figure 2 This is a schematic diagram of the segmented blocks;

[0024] Figure 3 This is a schematic diagram showing the distribution of black and white areas in the image.

[0025] Figure 4 This is a schematic diagram of the distance between ink droplets during charging. Detailed Implementation

[0026] A method for controlling ink droplet charging in QR code printing includes the following steps:

[0027] S1. After obtaining the original QR code image, divide the original QR code image into N columns of image blocks in a column-by-column manner;

[0028] S2. Scan and analyze each column of blocks sequentially to determine the position and coverage of the black and white areas on each column of blocks;

[0029] S3. Calculate the charging spacing corresponding to each black block and the charging power corresponding to each ink droplet within the block.

[0030] S4. During printing, select the corresponding ink droplets according to the charging spacing of each black area, and charge the selected ink droplets to the required power to complete the printing.

[0031] Specifically: such as Figure 1 As shown, after obtaining the original QR code image in step S1, a Cartesian coordinate system is established, the original QR code image is placed in the coordinate system, and then the original QR code image is divided into N columns of image blocks. In this way, the coordinate range of the area where each image block is located can be obtained.

[0032] Specifically: such as Figure 2As shown, in step S2, each pixel in the image block is first scanned to obtain the color value of each pixel. Then, white pixels and black pixels are distinguished according to the color value, so as to determine the coverage range of the white and black areas in each image block, i.e., the coordinate range.

[0033] In this embodiment, X consecutive ink droplets are defined as a group.

[0034] like Figure 3 As shown, taking the first column of the image as an example, this image contains three black areas: S1, S2, and S3. The larger the vertical coordinate of a pixel in a black area, the greater the charge of the corresponding ink droplet (because the vertical deflection angle of the ink droplet is positively correlated with the amount of charge it carries).

[0035] By controlling the charge level of the ink droplets, it can be determined which black area the ink droplets are directed to. The average charge level of ink droplets directed to area S1 is greater than that of ink droplets directed to area S2, and the average charge level of ink droplets directed to area S2 is greater than that of ink droplets directed to area S3.

[0036] To avoid the influence of Coulomb forces on charged ink droplets, when selecting droplets to be charged from each group, droplets that are as far apart as possible should be chosen. However, the greater the distance between the charging droplets, the more groups of droplets are needed to complete the same printing area. This obviously increases the printing time without changing the crystal oscillation frequency. Therefore, the selection of charging droplets (i.e., determining the spacing between adjacent charging droplets) should be considered in conjunction with the printing area and the degree of influence of Coulomb forces.

[0037] To reduce the influence of Coulomb force, when selecting ink droplets to be directed towards region S1 from a set of ink droplets, the spacing between the selected droplets should be the largest; when selecting ink droplets to be directed towards region S2, the spacing between the selected droplets should be slightly smaller; and when selecting ink droplets to be directed towards region S3, the spacing between the selected droplets should be the smallest.

[0038] Based on the above principles, for a set of ink droplets containing X number of ink droplets, the main issue to consider when selecting charging ink droplets is: how to determine the spacing between charging ink droplets directed towards each black area?

[0039] Taking region S1 as an example, first calculate the charging capacity corresponding to the minimum vertical coordinate point A and the maximum vertical coordinate point B in this region. The charging capacity corresponding to point A is Qa, and the charging capacity corresponding to point B is Qb.

[0040] Assuming the number of vertical pixels between points A and B is P, the charge difference between adjacent pixels in the vertical direction can be considered to be (Qa-Qb) / P. Based on this, the charging charge corresponding to each pixel between points A and B can be calculated.

[0041] The Coulomb force values ​​between the ink droplet at point A and the ink droplets at other pixels below point A are calculated using the Coulomb formula F=k*q1*q2 / d², thus obtaining the Coulomb force array in region S1.

[0042] Similarly, the Coulomb force arrays for regions S2 and S3 can be obtained.

[0043] The Coulomb force values ​​in the Coulomb force array of each black region are compared one by one with the preset Coulomb force reference value Fc, and the Coulomb force value Fz that is closest to Fc and smaller than Fc is found.

[0044] It should be noted that the value of Fc needs to be calibrated beforehand through extensive experiments. The value of Fc reflects the degree of influence of the Coulomb force between charged ink droplets. If the Coulomb force between charged ink droplets is greater than Fc, the trajectory of the charged ink droplets will be significantly affected by the Coulomb force between them; if the Coulomb force between charged ink droplets is less than Fc, the trajectory of the charged ink droplets will be basically unaffected by the Coulomb force between them.

[0045] Find the two pixels corresponding to the Coulomb force value Fz, and then determine the spacing between the ink droplets corresponding to these two pixels (i.e., how many uncharged ink droplets are between these two charged ink droplets). Define this spacing as the charging spacing of each black area.

[0046] Finally, when printing each black area, select the corresponding ink droplet according to the charging distance of each black area, charge the selected ink droplet to the required power, and complete the printing.

[0047] like Figure 4 As shown in the diagram, the first row of spheres represents a group of ejected ink droplets, hollow spheres represent uncharged ink droplets, and solid spheres represent charged ink droplets.

[0048] The spheres in the second row of the diagram represent the charging status of each group of ink droplets when printing in the S3 area. For example, if there is an uncharged ink droplet between two adjacent charged ink droplets, then the charging interval in the S3 area is one ink droplet.

[0049] Depend on Figure 4 It can also be seen that the charging spacing in area S2 is 2 ink droplets, and the charging spacing in area S3 is 3 ink droplets.

[0050] Since the vertical coordinate span of each black area is different (i.e., the area of ​​each black area is different), and the charging spacing corresponding to each black area is also different, if the method of printing one by one (i.e., printing one area first and then printing the next area) is used to form each black area, the time required to complete each black area individually (i.e., the number of ink droplet groups that need to be ejected) may vary greatly.

[0051] If the printing method is adopted one by one, the total time to complete the printing of the entire QR code may be relatively long. In order to further shorten the overall printing time of the QR code, this embodiment adopts the "cross" printing method.

[0052] Specifically: After determining the charging spacing of each black area, in step S4, some ink droplets corresponding to the black area with the smallest charging spacing are randomly inserted into the ink droplet groups of each black area with a larger charging spacing (the number of the original ink droplet groups remains unchanged, but some ink droplets are randomly changed into charging ink droplets), and the ink droplets are only inserted in the positions of the ink droplet groups with lower charging power.

[0053] The above measures can shorten the overall printing time and improve printing efficiency to a certain extent.

[0054] like Figure 3 As shown, when dividing the case into blocks, if the column width is relatively large, the resulting blocks may have inconsistent distribution of black areas on the left and right sides, such as in the third column.

[0055] This problem can be solved by increasing the number of columns and decreasing the column width.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling ink droplet charging in QR code printing, characterized in that, Includes the following steps: S1. After obtaining the original QR code image, divide the original QR code image into N columns of image blocks in a column-by-column manner; S2. Scan and analyze each column of blocks sequentially to determine the position and coverage of the black and white areas on each column of blocks; S3. Calculate the charging distance corresponding to each black patch and the charging amount corresponding to each ink droplet within the patch; first, calculate the charging amount corresponding to the minimum vertical coordinate point A and the maximum vertical coordinate point B within the black area, where the charging amount corresponding to point A is Qa and the charging amount corresponding to point B is Qb; if the number of vertical pixels between points A and B is P, then the charging amount difference between adjacent pixels in the vertical direction can be considered to be (Qa-Qb) / P; based on this, the charging amount corresponding to each pixel between points A and B can be calculated; then, using the Coulomb formula F=k*q1*q2 / d², the charging distance between the ink droplets at point A and point B can be calculated. By measuring the Coulomb force values ​​between the ink droplets at each of the other pixels below, a Coulomb force array within the black area is obtained. Repeating this process yields the Coulomb force arrays for all black areas within each column of the image. Then, the Coulomb force values ​​in each black area's Coulomb force array are compared one by one with the preset Coulomb force reference value Fc. The Coulomb force value Fz that is closest to Fc and smaller than Fc is found for each black area. The two pixels corresponding to the Coulomb force value Fz are then identified, and the distance between the ink droplets corresponding to these two pixels, i.e., the charging distance, can be determined, thus enabling the determination of the ink droplet charging distance for each black area. S4. During printing, select the corresponding ink droplets according to the charging spacing of each black area, and charge the selected ink droplets to the required power to complete the printing.

2. The ink droplet charging control method for QR code printing according to claim 1, characterized in that: After obtaining the original QR code image in step S1, a Cartesian coordinate system is established, the original QR code image is placed in the coordinate system, and then the original QR code image is divided into N columns of image blocks, so that the coordinate range of the area where each image block is located can be obtained.

3. The ink droplet charging control method for QR code printing according to claim 2, characterized in that: in In step S2, each pixel in the image block is scanned first to obtain the color value of each pixel. Then, white pixels and black pixels are distinguished based on the color value, so as to determine the coverage range of the white and black areas in each image block, i.e., the coordinate range.

4. The ink droplet charging control method for QR code printing according to claim 1, characterized in that: in After determining the charging spacing of each black area, in step S4, some ink droplets corresponding to the black area with the smallest charging spacing are randomly inserted into the ink droplet groups of each black area with a larger charging spacing, and the ink droplets are only inserted into the positions of the ink droplet groups with lower charging power.

Images